Use dataclass properties in xiaomi_miio discovery

[epenet]

Proposed change

Use dataclass properties in xiaomi_miio discovery.

Linked to #60540

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• Dependency upgrade
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[probot-home-assistant]

Hey there @rytilahti, @syssi, @starkillerOG, @bieniu, mind taking a look at this pull request as it has been labeled with an integration (xiaomi_miio) you are listed as a code owner for? Thanks!
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[epenet]

This succeeds in python 3.9 but fails in python 3.8. I don't see how my changes affect this.

[epenet]

No longer required (see #60561)