discussion all topics in breadcrumbs moved away from h6

lms/djangoapps/discussion/static/discussion/templates/fake-breadcrumbs.underscore

-<h6 class="hd-6 breadcrumbs">
+<div class="breadcrumbs">
     <span class="nav-item">
         <button class="btn-link all-topics">
             <span class="icon fa fa-bars" aria-hidden="true"></span><%- gettext('All Topics') %>
@@ -8,4 +8,4 @@
         <span class="fa fa-angle-right"></span>
         <span class="nav-item"><%- content %></span>
     <% }); %>
-</h6>
+</div>

lms/static/sass/discussion/elements/_navigation.scss

@@ -20,6 +20,13 @@
         vertical-align: middle;
     }
 
+    .has-breadcrumbs .breadcrumbs {
+        margin-bottom: ($baseline / 2);
+        font-size: font-size(base);
+        font-weight: font-weight(semi-bold);
+        line-height: $base-line-height;
+    }
+
     .page-header-main {
         line-height: $searchBoxHeight;
     }