bump gitlab runner to bb.6

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/gitlab-runner/-/blob/0.63.0-bb.6/CHANGELOG.md

Package MR

big-bang/product/packages/gitlab-runner!124 (merged)

For Issue

Closes big-bang/product/packages/gitlab#215 (closed)

Upgrade Notices

N/A