Fix warning in oss fuzz build (#5163)

Signed-off-by: Miguel Company <miguelcompany@eprosima.com>

src/cpp/rtps/messages/MessageReceiver.cpp

@@ -68,6 +68,7 @@ MessageReceiver::MessageReceiver(
  , crypto_payload_(participant->is_secure() ? rec_buffer_size : 0)
 #endif // if HAVE_SECURITY
 {
+ static_cast<void>(participant);
  (void)rec_buffer_size;
  EPROSIMA_LOG_INFO(RTPS_MSG_IN, "Created with CDRMessage of size: " << rec_buffer_size);