fix quiz index option button kebab styling

fixes QO-672
flag = none

Test Plan:
- Create a course and a quiz in the course (old quizzes)
- view the kebab button in the quizzes index for the newly created quiz
- Observe that the kebab button next to the quiz matches
  styling with the kebab next to the add quiz button
- Verify in all supported browsers

Change-Id: I8a66b83af1a08d7406ba9345ecd5d8be1bd10b77
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/254072
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Jared Crystal <jcrystal@instructure.com>
QA-Review: Mark McDermott <mmcdermott@instructure.com>
Product-Review: Susan Sorensen <susan.sorensen@instructure.com>

app/views/jst/quizzes/QuizItemView.handlebars

@@ -102,7 +102,7 @@
               <span data-view="publish-icon" class="publish-icon"></span>
           {{/if}}
           <div class="inline-block">
-            <button class="al-trigger al-trigger-gray" aria-haspopup="true" aria-owns="ui-id-{{id}}-1" role="button">
+            <button class="al-trigger al-trigger-gray btn" aria-haspopup="true" aria-owns="ui-id-{{id}}-1" role="button">
               <i class="icon-more" aria-hidden="true"></i>
               <span class="screenreader-only">{{#t}}Options for {{title_label}}{{/t}}</span>
             </button>