Update repositories.txt

Add AirNgin STM32 MQTT Client library

Author: AirNgin

repositories.txt

@@ -7676,5 +7676,4 @@ https://github.com/stacknix/stackmq-esp32
 https://github.com/marekburiak/ESP32_MQTTClient
 https://github.com/levkovigor/PTZProtocolHandler
 https://github.com/Alex-Stone-Github/pepstep
-https://github.com/AirNgin/Airngin-esp32-mqtt-client
 https://github.com/AirNgin/Airngin-stm32-mqtt-client