Fix websockets-disabled build with an ifdef. rs=mcmanus (No bug)

netwerk/build/nsNetModule.cpp

@@ -635,8 +635,10 @@ static void nsNetShutdown()
     // Release DNS service reference.
     nsDNSPrefetch::Shutdown();
 
+#ifdef NECKO_PROTOCOL_websocket
     // Release the Websocket Admission Manager
     mozilla::net::nsWebSocketHandler::Shutdown();
+#endif // NECKO_PROTOCOL_websocket
 }
 
 NS_DEFINE_NAMED_CID(NS_IOSERVICE_CID);