When using alias, we no longer can't nor need to prefix command with
git. This change updates all [alias] blocks and removes git from it.

Change-Id: Id89142ef86935e04e21872ce61fb63a511ed40a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3244473Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>