chore(deps): move futures to dev-deps

[Totodore]

Checklist

• I have read the Contributor Guide
• I have read and agree to the Code of Conduct
• I have added a description of my changes and why I'd like them included in the section below

Description of Changes

The futures crate bring a whole async executor whereas the only things that are used in this lib are :

• The Future trait which comes from the ̀futures-core lib and also exist in the std lib (MSRV 1.36)
• The Ready struct which comes from the futures-util lib and also exist in the std lib (MSRV 1.48)
• The ready macro which comes from the futures-core lib (and can be replaced with match statements).

Currently everything is either available in the std or can be replaced.

It might also be a good idea to define a msrv for this crate.

Related Issues

• Use futures-util rather than futures nats-io/nats.rs#1421

[fu5ha]

Thanks! I think this looks like a good change. I suppose this bumps our MSRV to at least 1.48. We don't explicitly document it but probably should, but 1.48 is old enough that I think I'm fine with just going for it.

[fu5ha]

If you could fix the clippy lint and also add a Changelog entry that would be great :)

[Totodore]

@fu5ha it seems that there is a flaky test that doesn't pass on windows. I tried to make a fix, it works well on my fork.

[fu5ha]

Nice, thank you! I will tag and publish a release soon

[fu5ha]

Published as 0.5.2