mattermost update to 10.5.1-bb.2

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/10.5.1-bb.2/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!296 (merged)

For Issue

Closes big-bang/product/packages/mattermost#196 (closed)

Upgrade Notices

n/a