[enzyme] Remove || in invoke logic

Author: chenesan

packages/enzyme/src/ReactWrapper.js

@@ -841,8 +841,9 @@ class ReactWrapper {
         throw new TypeError('ReactWrapper::invoke() requires the name of a prop whose value is a function');
       }
       return (...args) => {
-        const wrapAct = this[RENDERER].act || function wrapAct(fn) { return fn(); };
-        const response = wrapAct(() => handler(...args));
+        const response = typeof this[RENDERER].act === 'function'
+          ? this[RENDERER].act(() => handler(...args))
+          : handler(...args);
         this[ROOT].update();
         return response;
       };