Update git-drover to use branch CQ

Now that the CQ has been enabled for both the Beta and Stable
branches, git-drover should use the commit queue instead of
directly submitting the CL. To that end, this CL replaces the
usage of `git cl land` with `git cl set-commit`.

Change-Id: I0d0c10115acc98eafe0c069825de5499b8ade3e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1960697
Auto-Submit: Aaron Gable <agable@chromium.org>
Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>

git_drover.py

@@ -293,9 +293,9 @@ class _Drover(object):
                           error_message='Upload failed',
                           interactive=True)
 
-    if not self._confirm('About to land on %s.' % self._branch):
+    if not self._confirm('About to start CQ on %s.' % self._branch):
       return False
-    self._run_git_command(['cl', 'land', '--bypass-hooks'], interactive=True)
+    self._run_git_command(['cl', 'set-commit'], interactive=True)
     return True
 
   def _run_git_command(self, args, error_message=None, interactive=False):

tests/git_drover_test.py

@@ -70,7 +70,7 @@ class GitDroverTest(unittest.TestCase):
          self._target_repo),
     ]
     self.LAND_COMMAND = [
-        (['git', 'cl', 'land', '--bypass-hooks'], self._target_repo),
+        (['git', 'cl', 'set-commit'], self._target_repo),
     ]
     if os.name == 'nt':
       self.BRANCH_CLEANUP_COMMANDS = [