update baud rate to default circuitpython baud rate

Author: brentru

examples/adafruit_io_mqtt/adafruit_io_simpletest_cellular.py

@@ -25,10 +25,8 @@
     print("MQTT secrets are kept in secrets.py, please add them there!")
     raise
 
-# Create a serial connection for the FONA connection using 4800 baud.
-# These are the defaults you should use for the FONA Shield.
-# For other boards set RX = GPS module TX, and TX = GPS module RX pins.
-uart = busio.UART(board.TX, board.RX, baudrate=4800)
+# Create a serial connection for the FONA connection
+uart = busio.UART(board.TX, board.RX)
 rst = digitalio.DigitalInOut(board.D4)
 
 # Initialize FONA module (this may take a few seconds)