fix typo in comment

js/tests/index.html

@@ -13,7 +13,7 @@
     <script src="vendor/qunit.js"></script>
     <style>
       #qunit-tests > li.pass {
-        display: none;/* Make it easier to see failing tests is Sauce screencasts */
+        display: none;/* Make it easier to see failing tests in Sauce screencasts */
       }
 
       #qunit-fixture {