fixes for ruff

Author: Matthew Aitchison

tinker_cookbook/distillation/train_on_policy.py

@@ -7,7 +7,7 @@
 import logging
 import os
 import time
-from typing import Any, Dict, List, Literal, Sequence, cast
+from typing import Any, Dict, List, Sequence, cast
 
 import chz
 import tinker

tinker_cookbook/recipes/math_rl/train.py

@@ -1,7 +1,6 @@
 import asyncio
 import logging
 from datetime import datetime
-from typing import Literal
 
 import chz
 from tinker_cookbook import cli_utils, model_info

tinker_cookbook/rl/train.py

@@ -8,7 +8,7 @@
 import os
 import time
 from contextlib import contextmanager
-from typing import Any, Callable, Iterator, List, Literal, Sequence
+from typing import Any, Callable, Iterator, List, Sequence
 
 import chz
 import numpy as np