Bug 1383257 - JSReftest is green (only known intermittents), so doesn't need to be tier 3. r=kmoir

for: Land changes to flip windows nightlies on, and to tier 1 on central

MozReview-Commit-ID: AtBXyrPqRRI

--HG--
extra : rebase_source : a71b0c595d7b962fc150e74f3ba35445544f074d

taskcluster/ci/test/tests.yml

@@ -303,7 +303,6 @@ jsreftest:
     tier:
         by-test-platform:
             linux64-qr/.*: 1
-            windows10-64/.*: 3
             default: default
 
 marionette: