Correction to Homeassistant MQTT Discovery for Temp unit

[michaelsidenius]

Describe the bug
Homeassistant is giving a warning:

WARNING (MainThread) [homeassistant.components.sensor] Entity sensor.ams_d015_temp (<class 'homeassistant.components.mqtt.sensor.MqttSensor'>) is using native unit of measurement 'C' which is not a valid unit for the device class ('temperature') it is using; expected one of ['°C', '°F', 'K']; Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+mqtt%22

To Reproduce
Setup AMS reader to use a MQTT server with Homeassistant payload

Expected behavior
No Homeassistant warnings

Screenshots

Hardware information:

• Denmark
• Meter: Kampstrup
• Encryption enabled: Yes
• AMS reader: ESP8266
• M-bus adapter (if applicable):

Relevant firmware information:

• Version: v2.3.8
• MQTT: yes
• MQTT payload type: Homeassistant
• HAN GPIO: UART2
• HAN baud and parity: 2400 8N1
• Temperature sensors: NONE
• ENTSO-E API enabled: no

Additional context

[ArnieO]

Thank you for notifying us on that warning.
So HA wants the °-sign in addition to C.
OK - we'll put it on the list for a future update.