Allow for port 8883 due to slightly different setup

[makermelissa]

From @brentru:

return self.init_mqtt(IO_MQTT_BROKER, 1883, aio_username, aio_key, True)

Users may want to use secure port 8883. Setting up the client for the S2/SSL will be different and may need to be modified.

[makermelissa]

@brentru, do you have any examples for what is different?

[brentru]

Yes, please see the example for ESP32-S2 here: https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT/blob/master/examples/minimqtt_simpletest.py

Check out both the imports, and L75 through L86. MiniMQTT defaults to the secure port 8883, we should support that in this library by default.