Bump futures from 0.3.5 to 0.3.13

Bumps [futures](https://github.com/rust-lang/futures-rs) from 0.3.5 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@0.3.5...0.3.13)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Cargo.lock

@@ -19,7 +19,7 @@ chrono = { version = "0.4.19", features = ["serde"] }
 uuid = { version = "0.8.1", features = ["serde", "v4"] }
 unicode-width = "0.1.8"
 rand = "0.7.3"
-futures = "0.3.5"
+futures = "0.3.8"
 tokio = { version = "0.2.21", features = ["full"] }
 warp = "0.2.5"
 http-api-problem = { version = "0.17.0", features = ["with-warp"] }