mattermost update to 7.10.3-bb.1

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/mattermost/-/blob/7.10.3-bb.1/CHANGELOG.md

Package MR

big-bang/product/packages/mattermost!132 (merged)

For Issue

Closes https://repo1.dso.mil/big-bang/product/packages/mattermost/-/issues/75