Fix Minio SecurityContext for Mattermost

Fixes the securitycontext for Mattermost's deployment of Minio. See MR: https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/merge_requests/23. This is an issue that the Enterprise Collab team has been running into since the initial MM addon - previous fixes have been poorly tested and didn't work. Tested this fix on RKE2, k3d, and had several others test on RKE2. Also this fix makes sense, since the IB image user is 1001 for minio.

Closes #360 (closed)

.gitlab-ci/README.md.gotmpl

@@ -7,6 +7,8 @@
 
 {{ template "chart.homepageLine" . }}
 
+> _This is a mirror of a government repo hosted on [Repo1](https://repo1.dso.mil/) by [DoD Platform One](http://p1.dso.mil/).  Please direct all code changes, issues and comments to https://repo1.dso.mil/platform-one/big-bang/bigbang_
+
 Big Bang follows a [GitOps](#gitops) approach to configuration management, using [Flux v2](#flux-v2) to reconcile Git with the cluster.  Environments (e.g. dev, prod) and packages (e.g. istio) can be fully configured to suit the deployment needs.
 
 ## Usage