Bug 1547272 - ensure windows10-aarch64 is set to tier 2 for talos-bcv. r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D29003

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

taskcluster/ci/test/talos.yml

@@ -41,6 +41,7 @@ talos-bcv:
             default: ['mozilla-beta', 'trunk', 'try']
     tier:
         by-test-platform:
+            windows10-aarch64/.*: 2
             .*-qr/.*: 3  # this should be disabled but might run via try syntax anyway, so explicitly downgrade to tier-3
             default: default
     max-run-time: 1800