mattermost update to 11.4.0-bb.1

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/11.4.0-bb.1/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!348 (merged)

For Issue

Closes issue

Upgrade Notices

Mattermost is now leveraging our bb-common integration for network policies and istio-related resources. Please refer to this blog post for additional information on the integration.