Delete two Sidekiq reliable_fetcher flags

What does this MR do and why?

gitlab_sidekiq_enable_semi_reliable_fetcher

• The gitlab_sidekiq_enable_semi_reliable_fetcher flag was introduced by gitlab-foss!23854 (diffs) on 2018-12-17

• No associated FF state change issues at https://gitlab.com/gitlab-com/gl-infra/feature-flag-log/-/issues/?search=gitlab_sidekiq_enable_semi_reliable_fetcher&sort=created_date&state=all&label_name%5B%5D=host%3A%3Agitlab.com

• I confirmed it doesn't exist on GitLab.com:

  The feature gitlab_sidekiq_enable_semi_reliable_fetcher does not exist on gprd, but is default_enabled: true in their YAML definition.

gitlab_sidekiq_reliable_fetcher

• The gitlab_sidekiq_reliable_fetcher was introduced by 34687cf0 on 2018-09-12

• No associated FF state change issues at https://gitlab.com/gitlab-com/gl-infra/feature-flag-log/-/issues/?search=gitlab_sidekiq_reliable_fetcher&sort=created_date&state=all&label_name%5B%5D=host%3A%3Agitlab.com

• I confirmed it's enabled globally on GitLab.com

  

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changed milestone to %16.9

added maintenancepipelines typemaintenance labels

assigned to @rymai

added Engineering Productivity label

added backend label

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backend	@tvellishetty (UTC+5.5, 4.5 hours ahead of author)	@abdwdd (UTC+5.5, 4.5 hours ahead of author)

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Generated by Danger

E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for a7f096ff

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Verify      | 31     | 0      | 0       | 0     | 31    | ✅     |
| Plan        | 53     | 0      | 0       | 0     | 53    | ✅     |
| Create      | 53     | 0      | 12      | 5     | 65    | ✅     |
| Govern      | 65     | 0      | 1       | 0     | 66    | ✅     |
| Monitor     | 7      | 0      | 0       | 0     | 7     | ✅     |
| Data Stores | 31     | 0      | 1       | 0     | 32    | ✅     |
| Release     | 5      | 0      | 0       | 0     | 5     | ✅     |
| Package     | 21     | 0      | 2       | 0     | 23    | ✅     |
| Analytics   | 2      | 0      | 0       | 0     | 2     | ✅     |
| Manage      | 0      | 0      | 1       | 0     | 1     | ➖     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 268    | 0      | 17      | 5     | 285   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

e2e-package-and-test: test report for a7f096ff

expand test summary

+---------------------------------------------------------------------+
|                           suites summary                            |
+----------------+--------+--------+---------+-------+-------+--------+
|                | passed | failed | skipped | flaky | total | result |
+----------------+--------+--------+---------+-------+-------+--------+
| Plan           | 246    | 0      | 13      | 0     | 259   | ✅     |
| Create         | 534    | 12     | 93      | 16    | 639   | ❌     |
| Verify         | 138    | 0      | 27      | 0     | 165   | ✅     |
| Configure      | 1      | 0      | 9       | 0     | 10    | ✅     |
| Release        | 15     | 0      | 3       | 0     | 18    | ✅     |
| Package        | 226    | 0      | 17      | 18    | 243   | ✅     |
| Fulfillment    | 8      | 0      | 75      | 0     | 83    | ✅     |
| Data Stores    | 115    | 1      | 31      | 1     | 147   | ❌     |
| Govern         | 271    | 0      | 22      | 4     | 293   | ✅     |
| Systems        | 8      | 0      | 0       | 0     | 8     | ✅     |
| Manage         | 39     | 0      | 11      | 3     | 50    | ✅     |
| Monitor        | 36     | 0      | 13      | 0     | 49    | ✅     |
| Analytics      | 7      | 0      | 0       | 0     | 7     | ✅     |
| GitLab Metrics | 2      | 0      | 1       | 0     | 3     | ✅     |
| ModelOps       | 0      | 0      | 3       | 0     | 3     | ➖     |
| Secure         | 6      | 0      | 3       | 0     | 9     | ✅     |
| Growth         | 0      | 0      | 6       | 0     | 6     | ➖     |
+----------------+--------+--------+---------+-------+-------+--------+
| Total          | 1652   | 13     | 327     | 42    | 1992  | ❌     |
+----------------+--------+--------+---------+-------+-------+--------+

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@f61527ae

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@b1610925

changed the description

@dbalexandre @schin1 @stanhu I'd like to get your feedback on these removals as I'm not sure what would be the impact given the central place Sidekiq has in our architecture. Let's not rush on this one as I'm not familiar with the files I touched here. I welcome your expertise (or anyone else's expertise if needed) before we take any decision to delete these flags.

requested review from @dbalexandre, @schin1, and @stanhu

removed review request for @stanhu

removed review request for @dbalexandre

added 436 commits

• 463d0aee...1968f3f1 - 435 commits from branch master
• a7f096ff - Delete two Sidekiq reliable_fetcher flags

Compare with previous version

mentioned in commit gitlab-org-sandbox/gitlab-jh-validation@17cac1ef

approved this merge request

@schin1, thanks for approving this merge request.

This is the first time the merge request has been approved. To ensure we don't only run predictive pipelines, and we don't break master, a new pipeline will be started shortly.

Please wait for the pipeline to start before resolving this discussion and set auto-merge for the new pipeline. See merging a merge request for more details.

added pipeline:mr-approved label

removed review request for @schin1