apply clang-tidy modernize-use-override

Summary: Use clang-tidy to mechanically add missing `override` and remove redundant `virtual`.

Reviewed By: igorsugak

Differential Revision: D5211868

fbshipit-source-id: 4118c4c72f8ec3485507f69679f7e852b3eaeb73

folly/io/async/test/MockAsyncUDPSocket.h

@@ -22,7 +22,7 @@ namespace folly { namespace test {
 
 struct MockAsyncUDPSocket : public AsyncUDPSocket {
   explicit MockAsyncUDPSocket(EventBase* evb) : AsyncUDPSocket(evb) {}
-  virtual ~MockAsyncUDPSocket() {}
+  ~MockAsyncUDPSocket() override {}
 
   MOCK_CONST_METHOD0(address, const SocketAddress&());
   MOCK_METHOD1(bind, void(const SocketAddress&));