Prepare 17.2.6 release for gitlab-jh

Release issue: https://jihulab.com/gitlab-cn/release/tasks/-/issues/221

Summary

This MR prepares 17-2-stable-jh for 17.2.6.

Automated cherry-picking

Merge requests labeled Pick into 17.2 should be automatically picked into this MR.

Manual intervention

If merge requests cannot be picked automatically they have to be created manually targeting 17-2-stable-jh-patch-6.

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See also Patch Releases documentation.