Remove --update-shallow from git-cache.

R=hinoka@chromium.org
BUG=339171

Review URL: https://codereview.chromium.org/183643002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@253887 0039d316-1c4b-4281-b951-d872f2087c98

git_cache.py

@@ -218,7 +218,7 @@ def CMDpopulate(parser, args):
       _config(repo_dir)
       if options.depth and os.path.exists(os.path.join(repo_dir, 'shallow')):
         logging.warn('Shallow fetch requested, but repo cache already exists.')
-      fetch_cmd = ['fetch'] + v + ['--update-shallow', '--tags', 'origin']
+      fetch_cmd = ['fetch'] + v + ['--tags', 'origin']
       RunGit(fetch_cmd, filter_fn=filter_fn, cwd=repo_dir, retry=True)