Fix unreachable-break-or-return issue in proxygen/lib/http/session/test/HQSessionTestCommon.cpp +5

Summary:
LLVM has two warnings `-Wunreachable-code-return` and `-Wunreachable-code-break` which identify `return` and `break` statements that cannot be reached. These compromise readability, can be misleading, and may identify bugs. This diff removes such statements.

`break` was often used defensively in `switch` statements. We now have `-Wimplicit-fallthrough` [enabled globally](https://fb.workplace.com/groups/fbcode/posts/8021835991186503), which replaces this inexact practice with a compiler guarantee.

The compiler used to be less intelligent and would throw an error if a function didn't return the correct type after a `throw` statement. The compiler is smarter now, so this code is unnecessary. `-Wreturn-type` is enabled globally and prevents functions from ending without an appropriate return.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: dtolnay

Differential Revision: D79967323

fbshipit-source-id: 711a5a948d9205413ed65f7faf0a2bf6234e3307

Author: r-barnes

third-party/proxygen/src/proxygen/lib/http/session/test/HQSessionTestCommon.cpp

@@ -107,7 +107,6 @@ folly::Optional<std::pair<UnidirectionalStreamType, size_t>> parseStreamPreface(
       } else {
         return folly::none;
       }
-      break;
     default:
       break;
   }