build: Bump semver from 1.0.20 to 1.0.21 in /fuzz

Bumps [semver](https://github.com/dtolnay/semver) from 1.0.20 to 1.0.21.
- [Release notes](https://github.com/dtolnay/semver/releases)
- [Commits](https://github.com/dtolnay/semver/compare/1.0.20...1.0.21)

---
updated-dependencies:
- dependency-name: semver
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

fuzz/Cargo.lock

@@ -703,9 +703,9 @@ dependencies = [
 
 [[package]]
 name = "semver"
-version = "1.0.20"
+version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "836fa6a3e1e547f9a2c4040802ec865b5d85f4014efe00555d7090a3dcaa1090"
+checksum = "b97ed7a9823b74f99c7742f5336af7be5ecd3eeafcb1507d1fa93347b1d589b0"
 
 [[package]]
 name = "serde"