remove trailing comma in js object literal

Change-Id: If1d66971a39ee97352a2116c02564c2ccc2cdc3e
Reviewed-on: https://gerrit.instructure.com/2473
Reviewed-by: Brian Whitmer <brian@instructure.com>
Tested-by: Hudson <hudson@instructure.com>

public/javascripts/quiz_timing.js

@@ -43,5 +43,5 @@ var timing = {
       result.referenceOffset = (offsetDiff * 1000) + (myOffset * 60000);
     }
     return result;
-  },
-};
+  }
+};