gapps: Add AndroidMigratePrebuilt

* On Custom ROM's on Pixels, the downloading of
  this app by SetupWizard often hangs up,
  and needs to be restarted. Ship this to avoid
  that.

* Added to LOWMEM checkas it isn't necessary.

proprietary-files-common-nongrouper.txt

@@ -1 +1,2 @@
+-priv-app/AndroidMigratePrebuilt/AndroidMigratePrebuilt.apk;PRESIGNED
 -priv-app/SetupWizard/SetupWizard.apk;PRESIGNED