Fixes #5971

Removed auth_config from our script as we don't need to pass it to
devtools script any more.

The failure is due to devtools change:

commit	934836a6c5b1a3442db7f7197569fc1bbdcb8991	[log] [tgz]
author	Edward Lemur <ehmaldonado@chromium.org>	Mon Sep 09 20:16:54 2019
committer	Commit Bot <commit-bot@chromium.org>	Mon Sep 09 20:16:54 2019
tree	c6cb985aca378a2f816bb7d21a072394b1d4882a
parent	1e4d70d1dd0865b0ac824beccee70d3852705dd8 [diff]
git-cl: Remove unused auth configs.

auth_config is a Rietveld thing, so it's not necessary
in most of the code, except for triggering try bots.

Bug: 1001756
Change-Id: I0f243a297b05a43a61b052ba75c5886556e81b4e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1793018