feat: stray quote keep quote

[fatelei]

Summary

stray quote keep quote for python >= "3.7", fix #2551

Test Plan

rust playground: https://gist.github.com/rust-play/eebce903f361ab4b58d5c7c98f4a3537

[fatelei]

when i add test:

LenientVersionSpecifiers::from_str(">=\"3.6\"").unwrap().into();

there is a error: expected version to start with a number

[konstin]

PEP 508, the standard for the requirements, is a bit tricky here: The main version specifier must not have quotes, while the version specifiers in the markers must have quotes.

This is a correct requirement: numpy >=1.19; python_version >= "3.7"
This one is incorrect, we want to fix it up: numpy ">=1.19"; python_version >= "3.7"
But this one is also incorrect, the markers need quotes: numpy >=1.19; python_version >= 3.7

So when we see numpy ">=1.19"; python_version >= "3.7", we only want to remove the first set of quotes, not the second set of quotes.

[ibraheemdev]

I opened up #3214, which should address this. Thanks @fatelei for your initial work on this.