Fix use of inline code formatting

Author: tekktrik

adafruit_aws_iot.py

@@ -274,7 +274,7 @@ def publish(
 
  :param str topic: MQTT topic to publish to.
  :param payload: Data to publish to topic. Must be able to be converted
- to a string using `str()`
+ to a string using ``str()``
  :type payload: str|float|bytes
  :param int qos: Quality of service level for publishing