Fix app crash when payload is too large

Summary:
Fixes T40544233

Exceptions should be thrown by value, not as a pointer, or else catching by reference (the recommended practice) won't work.

Reviewed By: priteshrnandgaonkar

Differential Revision: D14243337

fbshipit-source-id: 28677d7f1b3c025b67fb945f30116f3b751a89a8

xplat/Flipper/FlipperConnectionManagerImpl.cpp

@@ -357,7 +357,7 @@ rsocket::Payload toRSocketPayload(dynamic data) {
         json.substr(0, 100) + "...";
     log(logMessage);
     DCHECK_LE(payloadLength, maxPayloadSize);
-    throw new std::length_error(logMessage);
+    throw std::length_error(logMessage);
   }
 
   return payload;