Bump futures-channel from 0.3.3 to 0.3.4 (#457)
Bump futures-channel from 0.3.3 to 0.3.4 (#457)

Bumps [futures-channel](https://github.com/rust-lang/futures-rs) from 0.3.3 to 0.3.4.
- [Release notes](https://github.com/rust-lang/futures-rs/releases)
- [Changelog](https://github.com/rust-lang/futures-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/futures-rs/compare/0.3.3...0.3.4)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
alex/otp-cop