TinyMCE: remove role=tab from the keyboard shortcuts help dialog.

See #33031.
Built from https://develop.svn.wordpress.org/trunk@33430


git-svn-id: http://core.svn.wordpress.org/trunk@33397 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/js/tinymce/plugins/wordpress/plugin.js

@@ -312,7 +312,7 @@ tinymce.PluginManager.add( 'wordpress', function( editor ) {
 			$wrap = dialog.$el.find( '.mce-wp-help' );
 
 			if ( $wrap[0] ) {
-				$wrap.attr( 'tabindex', '0' ).attr( 'role', 'tab' );
+				$wrap.attr( 'tabindex', '0' );
 				$wrap[0].focus();
 				$wrap.on( 'keydown', function( event ) {
 					// Prevent use of: page up, page down, end, home, left arrow, up arrow, right arrow, down arrow