chore: Run pyupgrade --py38-plus, remove mentions of lower python versions

[rafalkrupinski]

Didn't touch the travis file. I'm guessing it should be removed.

Fixes #37

[CaselIT]

looks ok, but we could add also 3.11 and 12

[rafalkrupinski]

I guess it closes #37 too

[vytas7]

As mentioned on another PR, we haven't decided yet how we are going to bundle or unbundle this into Falcon going forward, but let's follow Falcon's suit and don't hard-drop 3.7 yet.

I.e. we can keep saying in the README that we only support 3.8+, but python_requires should still allow 3.7.

[vytas7]

Let's resurrect 3.7 support in setup.cfg

[vytas7]

Thanks!

[rafalkrupinski]

I.e. we can keep saying in the README that we only support 3.8+, but python_requires should still allow 3.7.

I wouldn't like to introduce such difference between the readme and the config.

Also, running pyupgrade --py37-plus didn't introduce any changes versus --py-38-plus, so no code changes.

[vytas7]

I wouldn't like to introduce such difference between the readme and the config.

That's a valid point too, works both ways for me. python_requires is what is required for installation, but "support" might mean different things though, like support as in bug reports are considered for, etc.