Draft: Prepare 15.11.1 release for omnibus-gitlab-jh

Release issue: https://jihulab.com/gitlab-cn/release/tasks/-/issues/57

Summary

This MR prepares 15-11-stable-jh for 15.11.1.

Automated cherry-picking

Merge requests labeled ~"Pick into 15.11" should be automatically picked into this MR.

Manual intervention

If merge requests cannot be picked automatically they have to be created manually targeting 15-11-stable-jh-patch-1.

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See also Patch Releases documentation.