Mobile App using invalid unit of measurement for Battery entity

### The problem

After upgrading HA to `v2023.1.0` I startet to receive following log warnings:

```
Entity sensor.ismars_iphone_battery_state () is using native unit of measurement 'None' which is not a valid unit for the device class ('battery') it is using; 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+mobile_app%22
```

I have not manually configured this entity, so I guess this needs to be fixed in core.

### What version of Home Assistant Core has the issue?

2023.1.1

### What was the last working version of Home Assistant Core?

2022.12.6

### What type of installation are you running?

Home Assistant Container

### Integration causing the issue

Mobile App

### Link to integration documentation on our website

https://www.home-assistant.io/integrations/mobile_app/

### Diagnostics information

_No response_

### Example YAML snippet

_No response_

### Anything in the logs that might be useful for us?

```txt
Entity sensor.ismars_iphone_battery_state () is using native unit of measurement 'None' which is not a valid unit for the device class ('battery') it is using; 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+mobile_app%22
```

### Additional information

_No response_