Cleanup: Remove SyncServiceImpl::expect_sync_configuration_aborted_

It was only used in a single DCHECK, and IMO that one was more confusing
than helpful.

Bug: none
Change-Id: I5389c636a0115d192596386140d96a0d78f20640
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5401895


Auto-Submit: Marc Treib <treib@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Maksim Moskvitin <mmoskvitin@google.com>
Cr-Commit-Position: refs/heads/main@{#1278981}