mattermost update to 10.2.0-bb.3

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/10.2.0-bb.3/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!287 (merged)

For Issue

Closes (big-bang/product/packages/mattermost#181 (closed))

Upgrade Notices

N/A