Revert "Add feature flag for "no data" backup calls"

This reverts commit 27c64a3b.

Reason for revert: The GMSCore code to handle the flag will be part of DP2 and so we can remove the flag ahead of the cut.

GMSCore CL Status; https://cl-status.corp.google.com/#/summary/gmscore_prod/291378558
GMSCore Calendar; http://go/gms-schedule

Bug: 147481066
Test: m -j RunBackupFrameworksServicesRoboTests
Change-Id: I4159e064e739c6f366063c7fadd7cca40a7f07d9