Add retry: 2 to manifest-upload CI job

What does this MR do?

@madelacruz has been diligently helping me restart failed manifest-upload jobs so that ultimately they appear at https://gitlab-org.gitlab.io/omnibus-gitlab/gitlab-manifests/manifests.html which is then used to generate SBOMs. This MR adds retry: 2 to the manifest-upload job in gitlab-ci-config/dev-gitlab-org.yml to improve resilience against transient failures during manifest uploads. This improvement may however be insufficient but worth a shot for now.

Related issues

• Multiple omnibus manifests are missing (#9927 - closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• MR title and description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• Latest Merge Result pipeline is green.
• When ready for review, MR is labeled workflowready for review per the Distribution MR workflow.
• The UBT version and corresponding checksum hash have been updated and referenced in the merge request if applicable.
  • UBT EE pipeline (Trigger:ee-package-ubt) is green

For GitLab team members

• The manual Trigger:ee-package jobs have a green pipeline running against latest commit.
• If config/software or config/patches directories are changed, make sure the build-package-on-all-os job within the Trigger:ee-package downstream pipeline succeeded.
• If you are changing anything SSL related, then the Trigger:package:fips manual job within the Trigger:ee-package downstream pipeline must succeed.
• If CI configuration is changed, the branch must be pushed to dev.gitlab.org to confirm regular branch builds aren't broken.

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes.
• Documentation created/updated.
• Tests added.
• Integration tests added to GitLab QA.
• Equivalent MR/issue for the GitLab Chart opened.
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme[REDACTED]host:port may require quotation or other special handling when rendered in a template and written to a configuration file.