Bump futures from 0.3.12 to 0.3.13 (#230)

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.12 to 0.3.13.
- [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@0.3.12...0.3.13)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]