Bump paho-mqtt from 1.6.1 to 2.1.0 (#716)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -3,7 +3,7 @@ click==8.1.7
 crcmod==1.7
 getmac==0.9.5
 IntelHex==2.3.0
-paho-mqtt==1.6.1
+paho-mqtt==2.1.0
 pyserial==3.5
 pyserial-asyncio==0.6
 voluptuous==0.15.2