Accordion Example: Update documentation for change to button from lin…

…k (pull #477)

For issue #475, fix the roles, states, and properties table of the accordion example page.
Remove row for the button role on the `<a>` element and change the element column to button for the attributes applied to the button.

examples/accordion/accordion.html

@@ -270,34 +270,26 @@ <h2 id="rps_label">Role, Property, State, and Tabindex  Attributes</h2>
             </ul>
           </td>
         </tr>
-        <tr>
-          <th scope="row"><code>button</code></th>
-          <td></td>
-          <td><code>a</code></td>
-          <td>
-            Identifies the element as a button inside the accordion header that provides hide/show functionality.
-          </td>
-        </tr>
         <tr>
           <td> </td>
           <th scope="row"><code>aria-expanded=<q>true</q></code></th>
-          <td><code>a</code></td>
+          <td><code>button</code></td>
           <td>
             Set to <code>true</code> when the Accordion panel is expanded, otherwise set to <code>false</code>.
           </td>
         </tr>
         <tr>
           <td> </td>
           <th scope="row"><code>aria-controls=<q>ID</q></code></th>
-          <td><code>a</code></td>
+          <td><code>button</code></td>
           <td>
             Points to the ID of the panel which the header controls.
           </td>
         </tr>
         <tr>
           <td> </td>
           <th scope="row"><code>aria-disabled=<q>true</q></code></th>
-          <td><code>a</code></td>
+          <td><code>button</code></td>
           <td>
             If the accordion panel is expanded and is not allowed to be collapsed, then set to <code>true</code>.
           </td>