Add rviscomi to list of people cc-ed on metrics changelog.

Whenever we make a change to a metric, or see an unexpected regression,
my team will make a change to this directory. This auto-ccs rviscomi
so that he can update the corresponding CrUX documentation.

Change-Id: I204e6a674fd1cb9e385605b0c1331965ccadfbf0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008352Reviewed-by: Annie Sullivan <sullivan@chromium.org>
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Annie Sullivan <sullivan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733026}

WATCHLISTS

@@ -2652,6 +2652,7 @@
     'source_idls': ['jmedley+watch@chromium.org'],
     'speed_metrics_changelog': ['igrigorik@chromium.org',
                                 'kayce@chromium.org',
+                                'rviscomi@chromium.org',
                                 'sullivan@chromium.org'],
     'spellcheck': ['rlp+watch@chromium.org',
                    'rouslan+spell@chromium.org',