Update crostini-ui WATCHLISTS so components/exo goes to crostini-ui+exo

Changes to components/exo appear to be generally less relevant to Guest
OS than those matching cicerone|concierge|crostini|guest_os|plugin_vm.
This CL updates the WATCHLISTS so they will go to crostini-ui+exo,
allowing subscribers to filter these out.

Change-Id: Ib9bd2b3843589d03f3c127c89ebc52cd70cae03d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2454910
Auto-Submit: Timothy Loh <timloh@chromium.org>
Reviewed-by: Nic Hollingum <hollingum@google.com>
Commit-Queue: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814556}

WATCHLISTS

@@ -880,7 +880,6 @@
     },
     'crostini': {
       'filepath': 'cicerone'\
-                  '|components/exo'\
                   '|concierge'\
                   '|crostini'\
                   '|guest_os'\
@@ -975,6 +974,9 @@
                   'media/cdm/|' \
                   'third_party/widevine/cdm/'
     },
+    'exo': {
+      'filepath': 'components/exo',
+    },
     'explore_sites': {
       'filepath': 'chrome/browser/android/explore_sites/|' \
                   'chrome/android/java/src/org/chromium/chrome/browser/explore_sites/'
@@ -2464,6 +2466,7 @@
     'downloads_ui': ['dtrainor+watch@chromium.org'],
     'drive_resource_metadata': ['hashimoto+watch@chromium.org'],
     'eme': ['eme-reviews@chromium.org'],
+    'exo': ['crostini-ui+exo@chromium.org'],
     'explore_sites': ['chili+watch@chromium.org',
                       'dewittj+watch@chromium.org',
                       'dimich+watch@chromium.org',