Revert "sync: save any cruft after calling git gc."

This bug-cacher related code is no longer needed.

This reverts commit 891e8f72.

Change-Id: Ia94a2690ff149427fdcafacd39f5008cd60827d5
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/353774


Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Sam Saccone <samccone@google.com>
Tested-by: LaMont Jones <lamontjones@google.com>