Merge branch 'update-gitlab-shell-3-6-3' into 'master'

Update GITLAB_SHELL_VERSION to 3.6.3

Because VERSION at the gitlab-shell v3.6.2 tag was still 3.6.1: https://gitlab.com/gitlab-org/gitlab-shell/blob/v3.6.2/VERSION (my bad!)

VERSION at the v3.6.3 tag is now 3.6.3: https://gitlab.com/gitlab-org/gitlab-shell/blob/v3.6.3/VERSION

See merge request !6621

GITLAB_SHELL_VERSION

-3.6.2
+3.6.3

doc/update/8.12-to-8.13.md

@@ -72,7 +72,7 @@ sudo -u git -H git checkout 8-13-stable-ee
 ```bash
 cd /home/git/gitlab-shell
 sudo -u git -H git fetch --all --tags
-sudo -u git -H git checkout v3.6.2
+sudo -u git -H git checkout v3.6.3
 ```
 
 ### 6. Update gitlab-workhorse