Remove apex_pubkey from the bundle module

It's not yet supported by bundletool and blocks other testing (see
attached bug).

This is a partial revert of
https://android-review.googlesource.com/c/platform/build/soong/+/1183459/

Test: out/dist/mainline_modules_arm64/com.android.tzdata-base.zip
Test: checked content doesn't have apex_pubkey
Bug: 146460014
Change-Id: I268caa9f9736ba1913145a1ce1065f6f5179a6db