Bump futures-channel from 0.3.28 to 0.3.29

Bumps [futures-channel](https://github.com/rust-lang/futures-rs) from 0.3.28 to 0.3.29.
- [Release notes](https://github.com/rust-lang/futures-rs/releases)
- [Changelog](https://github.com/rust-lang/futures-rs/blob/master/CHANGELOG.md)
- [Commits](rust-lang/futures-rs@0.3.28...0.3.29)

---
updated-dependencies:
- dependency-name: futures-channel
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>