Mattermost: Switch minio subchart to oci

Package Merge Request

Package Changes

https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/blob/7.5.1-bb.2/CHANGELOG.md

Package MR

https://repo1.dso.mil/platform-one/big-bang/apps/collaboration-tools/mattermost/-/merge_requests/110