Revert "Pass --non-updatable-system flag to aapt2 when versionCode is unspecified"

This reverts commit ce320f86.

Reason for revert: <Dorid monitor: Likely culprit for b/347143262  - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.>

Change-Id: I70eabe014acc6feb123f28ac487f7d7d39e9fb6b