Update min LibCST version when it supports Python 3.9 relaxed decorator syntax

[Zac-HD]

with (a() as b, c() as d):
    pass

@(lambda f: f)
def g():
    pass

is valid Python 3.9 syntax which triggers psf/black#1948 and, in --refactor mode, Instagram/LibCST#486 and Instagram/LibCST#490. Once these upstream bugs are fixed, we should:

• update the minimum version of Black
• update the minimum version of LibCST

[Zac-HD]

Per Instagram/LibCST#285 (comment), an upcoming release will enable their new Rust-based parser for 3.10 & 3.11 grammar by default 🎉

(maybe this will also make it faster?)

[isidentical]

black also now supports 3.10+ syntax with patma / parenthesized with statements.

[Zac-HD]

shed now requires stable black (:tada::tada:) though I'm still waiting on psf/black#664 for #17 🙂

[Zac-HD]

This all works now; we just need to add some tests and bump the minimum required version.

[jpaniagua26]

I tried adding adding a test to check for python 3.9 syntax but it failed. Apparently libcst has not yet added syntax checking for this python version. https://github.com/jpaniagua26/shed/tree/python39syntax

[Zac-HD]

Closed by 6906329, released as shed == 23.05.2 🎉