Update to Actions usage in Enterprise Managed User namespace repositories

Enterprise Managed User namespace repositories were previously able to use GitHub-hosted Actions runners outside of the owning enterprise's entitlements. This was not an intentional configuration. Today we have disabled the ability for EMU user namespace repositories to use GitHub-hosted runners.

For customers using inner source workflows we recommend forking from an organization owned repository into your user namespace. You may then open a pull request back to the upstream repository and actions workflows will run as usual within the context of that organization and enterprise.

Learn more about enabling private repositories to run actions workflows from forks.