Fix bug in git_squash_branch.py.

main takes args starting from 1, not 0.

TBR=agable@chromium.org
BUG=261738

Review URL: https://codereview.chromium.org/212223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@259521 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/git_squash_branch.py b/git_squash_branch.py
index cbfb012..0e02539 100755
--- a/git_squash_branch.py
+++ b/git_squash_branch.py
@@ -17,4 +17,4 @@
   squash_current_branch(opts.message)
 
 if __name__ == '__main__':
-  sys.exit(main(sys.argv))
+  sys.exit(main(sys.argv[1:]))