remove useless ctor (#3989)

include/pybind11/functional.h

@@ -99,7 +99,7 @@ public:
             Return operator()(Args... args) const {
                 gil_scoped_acquire acq;
                 // casts the returned object as a rvalue to the return type
-                return object(hfunc.f(std::forward<Args>(args)...)).template cast<Return>();
+                return hfunc.f(std::forward<Args>(args)...).template cast<Return>();
             }
         };