Relax Python 3.8 version requirement

[provinzkraut]

Is your feature request related to a problem? Please describe.
Currently fakeredis requires Python >=3.8.1, which is incompatible with a lot of projects that have >=3.8 as a requirement.

Describe the solution you'd like
Unless there is a specific reason to target this specific version, it would be great to change the requirement to >=3.8.

Describe alternatives you've considered
N/A

Additional context
N/A

[cunla]

if I remember correctly, it is because of flake8 - but it is possible to change it to a dev dependency.

Do you want to change it?

[cunla]

See here

[provinzkraut]

@cunla Thanks for the quick fix!