Bump paho-mqtt from 1.6.1 to 2.1.0

Bumps [paho-mqtt](https://github.com/eclipse/paho.mqtt.python) from 1.6.1 to 2.1.0.
- [Release notes](https://github.com/eclipse/paho.mqtt.python/releases)
- [Changelog](https://github.com/eclipse/paho.mqtt.python/blob/master/ChangeLog.txt)
- [Commits](eclipse-paho/paho.mqtt.python@v1.6.1...v2.1.0)

---
updated-dependencies:
- dependency-name: paho-mqtt
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 adafruit-circuitpython-dht==4.0.4
-paho-mqtt==1.6.1
+paho-mqtt==2.1.0
 # pre-release to support raspberry pi 4
 # https://sourceforge.net/p/raspberry-gpio-python/tickets/190/
 rpi.gpio==0.7.1