Bug 1510536 - Enable Fennec wpt in CI as tier 2 jobs r=gbrown

Differential Revision: https://phabricator.services.mozilla.com/D13209

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

taskcluster/ci/test/test-sets.yml

@@ -349,7 +349,7 @@ android-x86-kvm-tests:
     # - mochitest-webgl1-core
     # - reftest
     # - test-verify
-    # - web-platform-tests
+    - web-platform-tests
     # - web-platform-tests-reftests
     # - web-platform-tests-wdspec
 

taskcluster/ci/test/web-platform.yml

@@ -49,7 +49,7 @@ web-platform-tests:
             default: built-projects
     tier:
         by-test-platform:
-            android.*: 3
+            android.*: 2
             linux64-asan/opt: 2
             linux64-qr/.*: 2  # can't be tier-1 if it's not running on integration branches
             default: default