Only show topics to revise if failed

ref-test/quiz/templates/quiz/result.html

@@ -30,7 +30,7 @@
         </div>
 
         {% if entry.results.grade == 'fail' %}
-            Unfortunately, you have not passed the theory exam in this attempt. For your next attempt, it might help to revise the following topics:
+            Unfortunately, you have not passed the theory exam in this attempt. For your next attempt, it might help to brush up on the following topics:
 
             <ul>
                 {% for tag in tag_output %}