Add arc-reviews+chromium@google.com for ARC related reviews.

BUG=b/74363217

Change-Id: I4aa4a2758772685df3b71f7ad334fa6e6fff745a
Reviewed-on: https://chromium-review.googlesource.com/974602Reviewed-by: Shuhei Takahashi <nya@chromium.org>
Commit-Queue: Junichi Uekawa <uekawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544967}

WATCHLISTS

@@ -1676,7 +1676,8 @@
             'hidehiko+watch@chromium.org',
             'lhchavez+watch@chromium.org',
             'victorhsieh+watch@chromium.org',
-            'yusukes+watch@chromium.org'],
+            'yusukes+watch@chromium.org',
+            'arc-reviews+chromium@google.com'],
     'arc_auth': ['khmel+watch@chromium.org'],
     'arc_fileapi': ['nya+watch@chromium.org'],
     'arc_kiosk': ['poromov+watch@chromium.org'],