Update html-aam/index.html

add note

Author: scottaohara

html-aam/index.html

@@ -13369,6 +13369,7 @@ <h4 id="att-popover">`popover`</h4>
                   <li>or when the element is a descendant of the `popover` and its `popovertarget` is the "`auto`" state.</li>
                 </ul>
                 <p>If specified on an element with an implicit role of `generic`, then the element's role instead maps to <a class="core-mapping" href="#role-map-group">`group`</a> for all <a data-cite="html/popover.html#the-popover-attribute">`popover` states</a>.</p>
+                <p class="note">There are no unique mappings for the different `popover` states. Any accessibility mapping changes for the popover element would be the responsibility of the author. e.g., using different base HTML elements, attributes, or ARIA attributes to make such changes.</p>
               </td>
             </tr>
           </tbody>