Update futures requirement from 0.1.25 to 0.3.30

Updates the requirements on [futures](https://github.com/rust-lang/futures-rs) to permit the latest version.
- [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@0.1.25...0.3.30)

---
updated-dependencies:
- dependency-name: futures
  dependency-type: direct:production
...

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

Cargo.toml

@@ -25,6 +25,6 @@ ureq = "2"
 
 [dev-dependencies]
 env_logger = { version = "0.11.3", default-features = false }
-futures = "0.1.25"
+futures = "0.3.30"
 hyper = "0.12"
 regex = "1.3"