Remove jquery.tabbable.shim

Closes #3278625

core/misc/jquery.tabbable.shim.js

-/**
- * @file
- * Defines a backwards-compatible shim for the jQuery UI :tabbable selector.
- */
-
-(($, Drupal, { isTabbable }) => {
-  $.extend($.expr[':'], {
-    tabbable(element) {
-      Drupal.deprecationError({
-        message:
-          'The :tabbable selector is deprecated in Drupal 9.2.0 and will be removed in Drupal 11.0.0. Use the core/tabbable library instead. See https://www.drupal.org/node/3183730',
-      });
-
-      return isTabbable(element);
-    },
-  });
-})(jQuery, Drupal, window.tabbable);