Relax types in traverseAsync etc.

[cmeeren]

I have always had my own Option.traverseAsync whose signature is f: ('T -> Async<'U>) -> opt: Option<'T> -> Async<Option<'U>>. Now my code is picking up the one from FsToolkit.ErrorHandling, whose signature is f: ('T -> Async<'T>) -> opt: Option<'T> -> Async<Option<'T>>. It unnecessarily restricts the output type to be the same as the input type.

This may apply to other similar traversals.

[TheAngryByrd]

Yeah, that seems like an oversight. Would you send a PR?

[cmeeren]

Sorry, I'm completely swamped.