Add note about submit buttons to popovertarget comments

a note to reference what is already defined in the HTML spec

html-aam/index.html

@@ -13453,6 +13453,10 @@ <h4 id="att-popovertarget">`popovertarget`</h4>
                   <li>The element's `popovertargetaction` attribute is the "`auto`" state and the element is a descendant of the `popover` it is associated with.</li>
                   <!-- accessibility sibling will be defined in the ARIA specification -->
                 </ul>
+                <p class="note">
+                  A button that represents a <a data-cite="html/forms.html#concept-submit-button">submit button</a> with a 
+                  <a data-html="html/form-control-infrastructure.html#form-owner">form owner</a> cannot invoke a popover.
+                </p>
               </td>
             </tr>
           </tbody>