chore(deps): update tokenizers requirement from 0.20.1 to 0.21.0

Updates the requirements on [tokenizers](https://github.com/huggingface/tokenizers) to permit the latest version.
- [Release notes](https://github.com/huggingface/tokenizers/releases)
- [Changelog](https://github.com/huggingface/tokenizers/blob/main/RELEASE.md)
- [Commits](huggingface/tokenizers@v0.20.1...v0.21.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -40,7 +40,7 @@ color-eyre = "0.6.3"
 rand = "0.8.5"
 regex = "1.11.0"
 serde_json = "1.0.129"
-tokenizers = { version = "0.20.1", features = ["hf-hub", "http"] }
+tokenizers = { version = "0.21.0", features = ["hf-hub", "http"] }
 tokio = { version = "1.40.0", features = ["rt-multi-thread"] }
 
 [package.metadata.docs.rs]