Update Condvar docs to use match ergonomics

[KevinWMatthews]

In std::sync::Condvar's docs, it looks like line 39:

let &(ref lock, ref cvar) = &*pair2;

and line 51

let &(ref lock, ref cvar) = &*pair;

were written before the match ergonomics RFC was merged.

Is it reasonable/preferable to change these lines to leverage match ergonomics? They would become:

let (lock, cvar) = &*pair2;

and

let (lock, cvar) = &*pair

respectively.

[jonas-schievink]

Sounds like a good idea to me. This should probably also be done for all the examples on that type (there's quite a lot using this pattern). Want to send a PR?

[KevinWMatthews]

@jonas-schievink Sure! It will give me an excuse to read all of the Condvar documentation in detail.

[Amanieu]

Fixed by #62942