Allow Python > 3.8

[laurensvalk]

We currently require python = "~3.8", so users with 3.9 have to install pyenv.

@dlech , I think we did this due to a limitation in bleak at the time. Do you know if this has been resolved?

[dlech]

No, it hasn't been resolved yet.

[dlech]

Would also be nice to change the minimum version to 3.7 for Raspberry Pi: pybricks/support#342

[dlech]

Bleak should be ready for 3.9 in the next release, whenever that is (could be sooner than later).

[dlech]

Fixed in https://github.com/pybricks/pybricksdev/releases/tag/v1.0.0-alpha.10