Document that 'manual' is mutually exclusive of other tooltip/popover triggers

Closes #16122
[skip sauce]

docs/_includes/js/popovers.html

@@ -229,7 +229,7 @@ sagittis lacus vel augue laoreet rutrum faucibus.">
           <td>trigger</td>
           <td>string</td>
           <td>'click'</td>
-          <td>How popover is triggered - click | hover | focus | manual. You may pass multiple triggers; separate them with a space.</td>
+          <td>How popover is triggered - click | hover | focus | manual. You may pass multiple triggers; separate them with a space. <code>manual</code> cannot be combined with any other trigger.</td>
         </tr>
         <tr>
           <td>viewport</td>

docs/_includes/js/tooltips.html

@@ -195,7 +195,7 @@ $('#example').tooltip(options)
           <td>trigger</td>
           <td>string</td>
           <td>'hover focus'</td>
-          <td>How tooltip is triggered - click | hover | focus | manual. You may pass multiple triggers; separate them with a space.</td>
+          <td>How tooltip is triggered - click | hover | focus | manual. You may pass multiple triggers; separate them with a space. <code>manual</code> cannot be combined with any other trigger.</td>
         </tr>
         <tr>
           <td>viewport</td>