Bug 1521099 - Promote raptor pageload geckoview tp6m-1 to tier 2; r=davehunt

Differential Revision: https://phabricator.services.mozilla.com/D17147

--HG--
extra : moz-landing-system : lando

taskcluster/ci/test/raptor.yml

@@ -352,8 +352,8 @@ raptor-tp6m-1-geckoview:
     try-name: raptor-tp6m-1-geckoview
     treeherder-symbol: Rap(tp6m-1)
     target: geckoview_example.apk
-    run-on-projects: ['try', 'mozilla-central']
-    tier: 3
+    run-on-projects: built-projects
+    tier: 2
     mozharness:
         extra-options:
             - --test=raptor-tp6m-1