Bump futures from 0.3.18 to 0.3.19

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.18 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@0.3.18...0.3.19)

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

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

Cargo.toml

@@ -20,7 +20,7 @@ tokio = { version = "~1.8", features = ["fs", "io-util", "time"] }  # LTS
 sha2 = "0.9.8"
 bytes = "1"
 base64 = "0.13.0"
-futures = "0.3.18"
+futures = "0.3.19"
 nix = "0.23.0"
 rusoto_core = { version = "0.47.0", default-features = false }
 rusoto_credential = "0.47.0"