fix: restore create_pretrained_tokenizer import

* Add back the import that was lost in merge
* This import is needed for custom tokenizer initialization

openhands/llm/llm.py

@@ -26,6 +26,7 @@
     ServiceUnavailableError,
 )
 from litellm.types.utils import CostPerToken, ModelResponse, Usage
+from litellm.utils import create_pretrained_tokenizer
 
 from openhands.core.exceptions import CloudFlareBlockageError
 from openhands.core.logger import openhands_logger as logger