Update tower requirement from 0.4 to 0.5

Updates the requirements on [tower](https://github.com/tower-rs/tower) to permit the latest version.
- [Release notes](https://github.com/tower-rs/tower/releases)
- [Commits](tower-rs/tower@tower-0.4.0...tower-0.5.0)

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

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

Author: dependabot[bot]

tower-cgi/Cargo.toml

@@ -8,7 +8,7 @@ license = "Apache-2.0"
 cgi-rs = { path = "../cgi-rs" }
 hyper = { version = "0.14", default-features = false }
 snafu = "0.8"
-tower = { version = "0.4", default-features = false, features = ["util"] }
+tower = { version = "0.5", default-features = false, features = ["util"] }
 
 [dev-dependencies]
 axum = "0.6"