Remove PEP references in Typing Python Libraries guide

[srittau]

The Typing Python Libraries (and possibly other guides) contains quite a few references to specific PEPs. These links should probably point to other guides, the Python documention, or the typing spec, instead.

[Anujpandey12345]

@srittau I want to work on this issue can you assign me this issue ?

[BHUVANSH855]

Hi @srittau,

I’d like to check if this issue is still open and needs work.

I’m interested in contributing to this and would be happy to work on a fix if it’s still pending. Please let me know if there’s any ongoing discussion or if someone is already working on it.

Thanks!