Use gitlab-shell v3.6.2 (GIT TRACE logging)

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 v 8.13.0 (unreleased)
+  - Use gitlab-shell v3.6.2 (GIT TRACE logging)
   - Speed-up group milestones show page
 v 8.12.2 (unreleased)

GITLAB_SHELL_VERSION

-3.6.0
+3.6.2