build: Bump clap from 3.2.22 to 4.0.9

Bumps [clap](https://github.com/clap-rs/clap) from 3.2.22 to 4.0.9.
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](clap-rs/clap@v3.2.22...v4.0.9)

---
updated-dependencies:
- dependency-name: clap
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Moving to the major version 4 introduced some breaking changes which had
to be handled manually.

Fixes #4709

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vhost_user_block/src/main.rs

@@ -26,11 +26,11 @@ fn main() {
             Arg::new("block-backend")
                 .long("block-backend")
                 .help(vhost_user_block::SYNTAX)
-                .takes_value(true)
+                .num_args(1)
                 .required(true),
         )
         .get_matches();
 
-    let backend_command = cmd_arguments.value_of("block-backend").unwrap();
+    let backend_command = cmd_arguments.get_one::<String>("block-backend").unwrap();
     start_block_backend(backend_command);
 }