Fix accessibility issue with empty <th> by switching to a <td>

Author: tdonohue

src/app/statistics-page/statistics-table/statistics-table.component.html

@@ -10,7 +10,7 @@ <h3 class="m-1">
     <tbody>
 
     <tr>
-      <th scope="col"></th>
+      <td></td>
       <th scope="col"
           *ngFor="let header of headers"
           class="{{header}}-header">