Update GitLab-Shell to v13.9.0

Upstream changelog: https://gitlab.com/gitlab-org/gitlab-shell/-/blob/6da1094b190a76231ec6d4ee4f0a0846de916446/CHANGELOG#L1-4

Update GitLab-Shell to v13.9.0
5d8d2536 · Zeger-Jan van de Weg · 9e8fc4be · 5d8d2536 · 5d8d2536
--- a/GITLAB_SHELL_VERSION
+++ b/GITLAB_SHELL_VERSION
-13.8.0
+13.9.0
--- a/changelogs/unreleased/zj-bump-shell.yml
+++ b/changelogs/unreleased/zj-bump-shell.yml
+---
+title: Update GitLab-Shell to v13.9.0
+merge_request: 45358
+author:
+type: changed