Remove extraneous semicolon from proxygen/lib/http/session/HTTPTransa…

…ction.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: D51631142

fbshipit-source-id: b76a26b190524b3e182d5a2cc8b38ed2b5469e37

proxygen/lib/http/session/HTTPTransaction.cpp

@@ -47,7 +47,8 @@ HTTPException stateMachineError(HTTPException::Direction dir, std::string msg) {
     invariantViolation(                                                   \
         HTTPException(HTTPException::Direction::INGRESS_AND_EGRESS, #X)); \
     return Y;                                                             \
-  }
+  }                                                                       \
+  static_assert(true, "semicolon required")
 
 #define INVARIANT(X)                                                      \
   if (!(X)) {                                                             \