fix casing

source

@@ -53535,7 +53535,7 @@ interface <dfn interface>HTMLButtonElement</dfn> : <span>HTMLElement</span> {
      <td><dfn data-x="attr-button-command-show-modal-state">Show Modal</dfn>
      <td>Opens the targeted <code>dialog</code> element as modal.
     <tr>
-     <td>A <span data-x="attr-button-command-custom">Custom command keyword</span>
+     <td>A <span data-x="attr-button-command-custom">custom command keyword</span>
      <td><dfn data-x="attr-button-command-custom-state">Custom</dfn>
      <td>Only dispatches the <code data-x="event-command">command</code> event on the targeted
      element.