backstage update to 2.6.3-bb.3

Package Merge Request

Package Changes

https://repo1.dso.mil/big-bang/product/packages/backstage/-/blob/2.6.3-bb.3/CHANGELOG.md

Package MR

big-bang/product/packages/backstage!97 (merged)

For Issue

Closes (big-bang/product/packages/backstage#93 (closed))

Upgrade Notices

(Include any relevant notes about upgrades here or write N/A if there are none)