Delete the search_scroll_api_increase_throughput feature flag

This feature flag has been validated with a search migration in production and it is safe to remove.

Rollout issue: #569700 (closed)

Remaining mentions of the feature flag (click to expand)

ee/spec/workers/concerns/search/elastic/migration_reindex_based_on_schema_version_spec.rb
210:        # TODO: removed from shared_examples as search_scroll_api_increase_throughput was removed

Currently the feature flag is enabled on production

It is possible that this MR will still need some changes to remove references to the feature flag in the code. At the moment the gitlab-housekeeper is not always capable of removing all references so you must check the diff and pipeline failures to confirm if there are any issues. It is the responsibility of groupglobal search to push those changes to this branch.

Note: If you do not want to remove this feature flag at this time, you can add an intended_to_rollout_by_date attribute in the feature flag YAML file to prevent automated removal.

TODO for the reviewers before merging this MR

• See the status of the rollout by checking #569700 (closed), https://gitlab.com/gitlab-com/gl-infra/feature-flag-log/-/issues/?search=search_scroll_api_increase_throughput&sort=created_date&state=all&label_name%5B%5D=host%3A%3Agitlab.com
• Verify the feature flag status via chatops by running /chatops run feature get search_scroll_api_increase_throughput.
• Search for references to SearchScrollApiIncreaseThroughput in frontend part of code
• Search for references to search_scroll_api_increase_throughput in code
• Check if we need to remove any Gem or other related code by looking at the changes in !204587 (merged)

This change was generated by gitlab-housekeeper locally using the Keeps::DeleteOldFeatureFlags keep.

To provide feedback on your experience with gitlab-housekeeper please create an issue with the label GitLab Housekeeper and consider pinging the author of this keep.