mattermost update to 9.10.1-bb.3

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/9.10.1-bb.3/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!266 (merged)

For Issue

Closes big-bang/product/packages/mattermost#167 (closed)

Upgrade Notices

n/a