Bug 1291954 followup, revert the part of changeset 2db29775e18f which prematurely declared SM(tsan) tier-1

MozReview-Commit-ID: 4o1lqWtVhNz

taskcluster/ci/spidermonkey/kind.yml

@@ -155,6 +155,7 @@ jobs:
             job-name: sm-tsan-opt
         treeherder:
             symbol: SM-tc(tsan)
+            tier: 3
         run-on-projects: []
         run:
             spidermonkey-variant: tsan