Set default createNotes to false

Disabling automatic note creation by default addresses two primary
concerns:
1. Admin Expectations: Most admins seeking a simple self-service
   interface for service accounts find automatic note generation
   unexpected and unnecessary for their workflow.
2. Performance: Reducing metadata overhead prevents impact on push
   times and Git operations (fetch/GC) on high-traffic, busy servers
   where excessive Git Notes can inflate the object database.

Change-Id: Ic1d449d926858c6add9972c79b5856bab46f9922