Fix disting of android_system.jar

The change I41b38d4828f8dc5d90dbb3ae59462812b8c036f2 accidentally
started disting the public android.jar to the path where the system
android.jar is expected.

Move the dist rules from the public stubs to the system stubs where
they belong.

Bug: 172937217
Test: m sdk dist && \
      zipinfo out/dist/apistubs/android/system/android.jar | \
      fgrep telecom/Phone.class
Change-Id: If20cb4ec32e1eb631a824ecc180d33c5088ff7c8