Change default netplay buffer to 5.

Source/Core/Core/NetPlayServer.cpp

@@ -36,7 +36,7 @@ NetPlayServer::NetPlayServer(const u16 port) : is_connected(false), m_is_running
 		m_do_loop = true;
 		m_selector.Add(m_socket);
 		m_thread = std::thread(&NetPlayServer::ThreadFunc, this);
-		m_target_buffer_size = 20;
+		m_target_buffer_size = 5;
 	}
 }