LEARNER-3128 add role=presentation to sequence nav list items

common/lib/xmodule/xmodule/js/fixtures/sequence.html

@@ -11,14 +11,14 @@
       </button>
       <nav class="sequence-list-wrapper" aria-label="Unit">
         <ol id="sequence-list" role="tablist">
-          <li>
+          <li role="presentation">
             <button role="tab" tabindex="0" aria-selected="true" aria-expanded="true" aria-controls="seq_content" class="seq_problem nav-item tab active" data-index="0" data-id="block-v1:edX+DemoX+Demo_Course+type@vertical+block@fb79dcbad35b466a8c6364f8ffee9050" data-element="1" data-page-title="Unit 101" data-path="Example Week 2: Get Interactive > Homework - Part 1  > Unit 101" id="tab_0">
               <span class="icon fa seq_problem" aria-hidden="true"></span>
               <span class="fa fa-fw fa-bookmark bookmark-icon is-hidden" aria-hidden="true"></span>
               <div class="sequence-tooltip sr"><span class="sr">problem</span>Unit 101<span class="sr bookmark-icon-sr"></span></div>
             </button>
           </li>
-          <li>
+          <li role="presentation">
             <button role="tab" tabindex="-1" aria-selected="true" aria-expanded="true" aria-controls="seq_content" class="seq_problem inactive nav-item tab" data-index="1" data-id="block-v1:edX+DemoX+Demo_Course+type@vertical+block@fb79dcbad35b466a8c6364f8ffee9051" data-element="2" data-page-title="Unit 102" data-path="Example Week 2: Get Interactive > Homework - Part 1 > Unit 102" id="tab_1">
               <span class="icon fa seq_problem" aria-hidden="true"></span>
               <span class="fa fa-fw fa-bookmark bookmark-icon is-hidden" aria-hidden="true"></span>

lms/templates/seq_module.html

@@ -24,8 +24,8 @@
     <nav class="sequence-list-wrapper" aria-label="${_('Sequence')}">
       <ol id="sequence-list" role="tablist">
         % for idx, item in enumerate(items):
-        <li>
-        <button class="seq_${item['type']} inactive nav-item tab"
+        <li role="presentation">
+          <button class="seq_${item['type']} inactive nav-item tab"
             role="tab"
             tabindex="-1"
             aria-selected="false"

lms/templates/ux/reference/fragments/unit-fragment.html

@@ -43,7 +43,7 @@
     </button>
     <nav class="sequence-list-wrapper" aria-label="Sequence">
         <ol id="sequence-list" role="tablist">
-            <li>
+            <li role="presentation">
                 <button class="seq_video nav-item tab active" role="tab" tabindex="0" aria-selected="true" aria-expanded="true" aria-controls="seq_content" data-index="0" data-id="block-v1:edX+DemoX+Demo_Course+type@vertical+block@vertical_0270f6de40fc" data-element="1" data-page-title="Introduction: Video and Sequences" data-path="Introduction > Demo Course Overview > Introduction: Video and Sequences" id="tab_0">
                     <span class="icon fa seq_video" aria-hidden="true"></span>
                     <span class="fa fa-fw fa-bookmark bookmark-icon is-hidden" aria-hidden="true"></span>