backstage update to 2.6.3-bb.2

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/backstage/-/blob/2.6.3-bb.2/CHANGELOG.md

Package MR

big-bang/product/packages/backstage!90 (merged)

For Issue

Closes issue

Upgrade Notices

Backstage is now leveraging our bb-common integration for network policies and istio-related resources. Please refer to this blog post for additional information on the integration.