Revert "Merge branch '373757-move-sidebar-items' into 'master'"

Purpose of revert

Revert !104047 (merged) to mitigate gitlab-org/release/tasks#5406 (closed)

Checklist

• Create an issue to reinstate the merge request and assign it to the author of the reverted merge request.
• [-] If the revert is to resolve a broken 'master' incident, please read through the Responsibilities of the Broken master resolution DRI.
• [-] If the revert involves a database migration, please read through Deleting existing migrations.
• Add the appropriate labels before the MR is created. We can skip CI/CD jobs only if the labels are added before the CI/CD pipeline is created.

Milestone info

• I am reverting something in the current milestone. No changelog is needed, and I've added a ~"regression:*" label.
• I am reverting something in a different milestone. A changelog is needed, and I've removed the ~"regression:*" label.

Related issues and merge requests