download .model files in exo bench (#1607)

## Motivation

failed again for kimi on a machine that had never downloaded it.

## Test Plan

### Manual Testing
it worked this time

bench/exo_bench.py

@@ -75,7 +75,7 @@ def load_tokenizer_for_bench(model_id: str) -> Any:
         model_path = Path(
             snapshot_download(
                 model_id,
-                allow_patterns=["*.json", "*.py", "*.tiktoken"],
+                allow_patterns=["*.json", "*.py", "*.tiktoken", "*.model"],
             )
         )