fixing vt spec

Author: fuzhenn

packages/vt/test/specs/update.spec.js

@@ -605,7 +605,9 @@ describe('update style specs', () => {
                 }
             });
             map.setZoom(map.getZoom() + 2);
-            assert(layer.getRenderer().getStyleCounter() === 2);
+            setTimeout(() => {
+                assert(layer.getRenderer().getStyleCounter() === 2);
+            }, 12);
         }, false, null, 0, 2);
     });