fix availability

[Thomas55555]

with Rest we found in the metadata, that the mower is not connected anymore. This information is still used for start-up of home assistant. But if the mower is not connected anymore, there are no update of the metadata, in the websocket. Regularly, the websocket is pushing an update every 14min. So if two updates are missing, we assume, that the mower is not available anymore.

[github-actions]

🎉 HACS repository validator action summary 🎉
✅ The repository is not archived
✅ manifest.json file exist
✅ All required keys are present in manifest.json
✅ hacs.json has the 'name' key set
✅ The repository has a description
✅ husqvarna_automower is added to https://github.com/home-assistant/brands NICE!
✅ The repository has topics
✅ The repository has issues enabled
✅ This day ends with an 'y' (Sunday)
✅ README.md exists
✅ Requirements validation
✅ HACS load check