build: bump clap from 3.2.20 to 3.2.21

Bumps [clap](https://github.com/clap-rs/clap) from 3.2.20 to 3.2.21.
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/v3.2.21/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/v3.2.20...v3.2.21)

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

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

vmm/Cargo.toml

@@ -22,7 +22,7 @@ arc-swap = "1.5.1"
 arch = { path = "../arch" }
 bitflags = "1.3.2"
 block_util = { path = "../block_util" }
-clap = "3.2.20"
+clap = "3.2.21"
 devices = { path = "../devices" }
 epoll = "4.3.1"
 event_monitor = { path = "../event_monitor" }