Bump futures-util from 0.3.17 to 0.3.19 (paritytech#10513)

Bumps [futures-util](https://github.com/rust-lang/futures-rs) from 0.3.17 to 0.3.19.
- [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@0.3.17...0.3.19)

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

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

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

utils/prometheus/Cargo.toml

@@ -15,7 +15,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 [dependencies]
 log = "0.4.8"
 prometheus = { version = "0.13.0", default-features = false }
-futures-util = { version = "0.3.17", default-features = false, features = ["io"] }
+futures-util = { version = "0.3.19", default-features = false, features = ["io"] }
 derive_more = "0.99"
 async-std = { version = "1.10.0", features = ["unstable"] }
 tokio = "1.15"