updating tokenizer version from 0.20.0 to 0.21.0 (mlc-ai#62)

Author: NaveenMittal0

rust/Cargo.toml

@@ -8,6 +8,6 @@ crate-type = ["staticlib"]
 
 [dependencies]
 
-tokenizers = { version = "0.20.0", default-features = false, features = ["onig"] }
+tokenizers = { version = "0.21.0", default-features = false, features = ["onig"] }
 serde = { version = "1.0", features = [ "derive" ] }
 serde_json = "1.0"