Update gitlab-shell to v13.4.0

Full list of changes:
https://gitlab.com/gitlab-org/gitlab-shell/-/blob/master/CHANGELOG

Closes https://gitlab.com/gitlab-org/gitlab-shell/-/issues/203

GITLAB_SHELL_VERSION

-13.3.0
+13.4.0

changelogs/unreleased/sh-upgrade-gitlab-shell-13-4-0.yml

+---
+title: Update gitlab-shell to v13.4.0
+merge_request: 37677
+author:
+type: changed