Accordion: Don't pass multiple classes to .toggleClass(). Fixes #6084…

… - Accordion: 1.8.5 not fully compatible with core 1.3.2.

ui/jquery.ui.accordion.js

@@ -92,7 +92,8 @@ $.widget( "ui.accordion", {
 
 		self.active = self._findActive( self.active || options.active )
 			.addClass( "ui-state-default ui-state-active" )
-			.toggleClass( "ui-corner-all ui-corner-top" );
+			.toggleClass( "ui-corner-all" )
+			.toggleClass( "ui-corner-top" );
 		self.active.next().addClass( "ui-accordion-content-active" );
 
 		self._createIcons();