Bump futures from 0.3.14 to 0.3.15 (#3178)

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.14 to 0.3.15.
- [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/0.3.14...0.3.15)

---
updated-dependencies:
- dependency-name: futures
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

polkadot/node/network/collator-protocol/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 always-assert = "0.1.2"
-futures = "0.3.12"
+futures = "0.3.15"
 futures-timer = "3"
 thiserror = "1.0.23"
 tracing = "0.1.26"