fix the delay bug

Code/Control/Laptop_Code/ESP32_slave/ESP32_slave.ino

@@ -316,5 +316,5 @@ void send_message(){
     Serial.println("Error sending the data");
   }
   //-------------------------------------------------------------------------------------
-  // delay(50); // delay 50 ms after send out the message 
+  delay(50); // delay 50 ms after send out the message 
 }