Remove lhchavez@ from WATCHLISTS

I'm not going going to be watching ARC-related changes going forward.

Bug: None
Change-Id: I606c46f81e39cf00ce7eb3611fc96c8a628730e2
Reviewed-on: https://chromium-review.googlesource.com/c/1258602Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Luis Hector Chavez <lhchavez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596071}

WATCHLISTS

@@ -1787,7 +1787,6 @@
              'tfarina@chromium.org'],
     'arc': ['elijahtaylor+arcwatch@chromium.org',
             'hidehiko+watch@chromium.org',
-            'lhchavez+watch@chromium.org',
             'victorhsieh+watch@chromium.org',
             'yusukes+watch@chromium.org',
             'arc-reviews+chromium@google.com'],