[docs] pointer::wrapping_sub has typo

[Lokathor]

The docs for pointer::wrapping_sub say

Calculates the offset from a pointer using wrapping arithmetic. (convenience for .wrapping_offset((count as isize).wrapping_sub()))

but they should say .wrapping_neg() instead

[jyn514]

@Lokathor are you interested in making a PR to fix it?

[Lokathor]

Josh you know I don't ever dare PR to rust-lang/rust ;3

[soniasingla]

@jyn514 can i take this bug? :)

[jyn514]

Go for it! The docs for this will be somewhere in library/, you can find them by hitting [src] in the docs. There are instructions for building at rustc-dev-guide.rust-lang.org/, the main command is x.py doc library/std.