Update index.html

Author: scottaohara

index.html

@@ -14352,7 +14352,7 @@ <h4 id=att-popovertarget>`popovertarget`</h4>
       <td>
         <p>
           User Agents MUST expose an <a class="core-mapping" href="#ariaDetails">`aria-details`</a> relation with the associated popover element
-          <strong>except</strong> under either of the following conditions:
+          <strong>except</strong> under the following conditions:
         </p>
         <ul>
           <li>The element's `popovertargetaction` attribute value is "`hide`"</li>