Merge branch 'Alexand-master-patch-21048' into 'master'

Add link to how to test KAS with TLS

See merge request https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/7530

Merged-by: Andrew Patterson <apatterson@gitlab.com>
Approved-by: Hossein Pursultani <hpursultani@gitlab.com>
Approved-by: Andrew Patterson <apatterson@gitlab.com>
Co-authored-by: João Alexandre Cunha <j.a.cunha@gmail.com>

Author: Andrew Patterson

test-plans/index.md

@@ -9,3 +9,7 @@
 - [Mattermost](upgrade-mattermost-testplan.md)
 - [redis](upgrade-redis-testplan.md)
 - [rubygems](upgrade-rubygems-testplan.md)
+
+## Other changes
+
+- [GitLab Agent for Kubernetes](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/-/blob/master/doc/test-multi-node-kas.md) on a multi-node setup with TLS communication between nodes.