Update clap requirement from 3.0.0 to 4.0.18

Updates the requirements on [clap](https://github.com/clap-rs/clap) to permit the latest version.
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/clap_complete-v3.0.0...v4.0.18)

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

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

Cargo.toml

@@ -10,7 +10,7 @@ authors = ["Frank Denis <github@pureftpd.org>"]
 edition = "2018"
 
 [dependencies]
-clap = { version = "3.0.0", features = ["std", "cargo", "wrap_help"] }
+clap = { version = "4.0.18", features = ["std", "cargo", "wrap_help"] }
 flate2 = "1"
 horrorshow = "0.8"
 hyper = "0.10"