Accessibility for delete on file upload question

Fixes CNVS-12798

test plan
- Setup a quiz with a file upload question
- Take the quiz
- Upload a file
- The delete (X) button in the file upload space should have proper
accessibility

Change-Id: Ib8dfe02cf020422609258c44ca9b3156148d8025
Reviewed-on: https://gerrit.instructure.com/37793
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Brian Finney <bfinney@instructure.com>

app/views/jst/quizzes/fileUploadQuestionState.handlebars

@@ -1,5 +1,5 @@
 {{#if display_name}}
-  {{display_name}}<a href="#" class="pull-right icon-end delete-attachment"></a>
+  {{display_name}}<a href="#" role='button' class="pull-right icon-end delete-attachment" aria-label='{{#t "#buttons.delete_file" name=display_name}}Delete file {{name}}{{/t}}'></a>
 {{else}}
   {{#if isIE}}
     <input name=file class="file-upload" type=file />