don't require package_name for non-override android_apps

For a non-override android_app, we can assume that the privapp_allowlist
already contains the correct package_name, and so we don't need to
overwrite it in this case.

Bug: 242509786
Test: go test
Merged-In: I0f137e34cae3478dc8b9178d138121ff1d936f07
Change-Id: I0f137e34cae3478dc8b9178d138121ff1d936f07