repo: do not update citc depot_tools

This shouldn't really happen, but who knows what users might
(accidentally) try to do.

Change-Id: Ic968f133693532a816b9bd3c8c5b97cba3261bc5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5309411
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Commit-Queue: Sergey Frolov <sfrolov@google.com>

repo

@@ -31,6 +31,8 @@ def _UpdateDepotTools():
     while path != path.parent:
         if (path / '.repo').is_dir() and (path / 'chromite').is_dir():
             return
+        if (path / '.citc').is_dir():
+            return
         path = path.parent
 
     if UPDATE_DEPOT_TOOLS.exists():