Upgrade paho-mqtt to 2.1.0

[luochen1990]

This package can not be build with latest NixOS, which provides paho-mqtt 2.1.0

Checking manifests ./custom_components/xiaomi_home/manifest.json

• paho-mqtt<2.0.0 not satisfied by version 2.1.0

Hoping for an upgrade.

Related Docs: https://eclipse.dev/paho/files/paho.mqtt.python/html/migrations.html