bot_update: Disable metrics collection for bots, since it's not supported.

Change-Id: Iee0b783d725f15fbe3ab3d41ce2303a2ab1807af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1713218Reviewed-by: Andy Perelson <ajp@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -313,6 +313,8 @@ def call_gclient(*args, **kwargs):
   """
   cmd = [sys.executable, '-u', GCLIENT_PATH]
   cmd.extend(args)
+  # Disable metrics collection on bots, since it's not supported anyway.
+  kwargs.setdefault('env', {})['DEPOT_TOOLS_METRICS'] = '0'
   return call(*cmd, **kwargs)