fixup! dgram: make UDPWrap more reusable

Author: addaleax

src/udp_wrap.h

@@ -151,7 +151,7 @@ class UDPWrap final : public HandleWrap,
   void OnRecv(ssize_t nread,
               const uv_buf_t& buf,
               const sockaddr* addr,
-              unsigned int flags);
+              unsigned int flags) override;
   ReqWrap<uv_udp_send_t>* CreateSendWrap(size_t msg_size) override;
   void OnSendDone(ReqWrap<uv_udp_send_t>* wrap, int status) override;