Rename vibration_pipeline_enabled flag

The flag was previously submitted as a non bugfix flag, so it cannot be
changed to a bugfix flag.

Bug: 344494220
Flag: android.os.vibrator.vibration_pipeline_fix_enabled
Test: VibratorManagerServiceTest
Change-Id: I437a2255fa9818384b02dfd56b8b83c5ebe8a6dc