Remove extraneous semicolon from folly/io/async/AsyncSocket.cpp

Summary:
Extraneous semicolons are a code smell and can mask more serious problems. `-Wextra-semi-stmt` finds them.

This diff removes an extraneous semicolon or adjusts a macro so that a semicolon is required after the macro (making it look like a standard function).

This file is drawn from a heavy-hitting list, so fixing this problem will allow *many* other files to take advantage of the safety `-Wextra-semi-stmt` offers.

This should be a low-risk diff: if it compiles, it works.

Reviewed By: meyering

Differential Revision: D51631129

fbshipit-source-id: 744ea519bab352dc1c575c44ec5d16777d03a648

folly/io/async/AsyncSocket.cpp

@@ -3283,7 +3283,7 @@ void AsyncSocket::handleRead() noexcept {
         break;
       case ReadCode::READ_DONE:
         return;
-    };
+    }
   }
 
   if (readCallback_ && eventBase_ == originalEventBase) {