Remove double bottom border on sub header

The table includes a border between the two making this unnecessary

docs/examples/dashboard/index.html

@@ -89,7 +89,7 @@
             </div>
           </div>
 
-          <h2 class="sub-header">Section title</h2>
+          <h2>Section title</h2>
           <div class="table-responsive">
             <table class="table table-striped">
               <thead>