Remove Leopard support from the flakiness dashboard

Remove Leopard support from the flakiness dashboard
https://bugs.webkit.org/show_bug.cgi?id=90390

Reviewed by Adam Barth.

* TestResultServer/static-dashboards/flakiness_dashboard.js:
(nonChromiumPlatform):
(chromiumPlatform):
* TestResultServer/static-dashboards/flakiness_dashboard_unittests.js:
(test):
* TestResultServer/static-dashboards/run-embedded-unittests.html:
* TestResultServer/static-dashboards/run-unittests.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121696 268f45cc-cd09-0410-ab3c-d52691b4dbfc