[Question] AICS - Gain Setting values/format

Hi,

I noticed that in `bumble/profiles/aics.py` the specified range for `Gain Setting Properties` characteristic is from 0 to 255, while the specification states it should be within -128 to 127 range.

Is that implementation intentional or is that a mistake?

For the reference see [3.2. Gain Setting Properties](https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/20509-AICS-html5/out/en/index-en.html#UUID-3bc93a2d-3f3f-0aaa-886f-d2602b6e0e51) and [Table 3.6: Set Gain Setting format ](https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/20509-AICS-html5/out/en/index-en.html#UUID-2b31d186-8474-8c1e-94bd-57636457babf)