Gob already supports branch redirect so we no longer need this in
depot_tools.

R=gavinmak@google.com

Change-Id: I0e697b022dc132bc5cba95e1b1746c0d72fe16aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3137816
Auto-Submit: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>