Merge branch 'sh-bump-gitlab-shell-8.12' into 'master'

Bump gitlab-shell upgrade version to 3.6.0 for 8.12

[ci skip]

Closes #22442

See merge request !6469

doc/update/8.11-to-8.12.md

@@ -70,7 +70,7 @@ sudo -u git -H git checkout 8-12-stable-ee
 ```bash
 cd /home/git/gitlab-shell
 sudo -u git -H git fetch --all --tags
-sudo -u git -H git checkout v3.5.0
+sudo -u git -H git checkout v3.6.0
 ```
 
 ### 6. Update gitlab-workhorse