mattermost update to 10.6.1-bb.4

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/10.6.1-bb.4/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!304 (merged)

For Issue

Closes (big-bang/product/packages/mattermost#206 (closed))

Upgrade Notices

(Include any relevant notes about upgrades here or write "N/A" if there are none) N/A