Cleanup example (#27059)

Extra argument does nothing.

examples/webgl_shadow_contact.html

@@ -214,7 +214,7 @@
 
 				} );
 
-				gui.add( state, 'showWireframe', true ).onChange( function () {
+				gui.add( state, 'showWireframe' ).onChange( function () {
 
 					if ( state.showWireframe ) {