build: Bump serde from 1.0.203 to 1.0.208

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.203 to 1.0.208.
- [Release notes](https://github.com/serde-rs/serde/releases)
- [Commits](https://github.com/serde-rs/serde/compare/v1.0.203...v1.0.208)

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

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

vmm/Cargo.toml

@@ -62,7 +62,7 @@ pci = { path = "../pci" }
 range_map_vec = { version = "0.2.0", optional = true }
 rate_limiter = { path = "../rate_limiter" }
 seccompiler = "0.4.0"
-serde = { version = "1.0.197", features = ["derive", "rc"] }
+serde = { version = "1.0.208", features = ["derive", "rc"] }
 serde_json = "1.0.120"
 serial_buffer = { path = "../serial_buffer" }
 signal-hook = "0.3.17"