Refactor comment on tool_choice for clarity

Split long comment about tool_choice into multiple lines for better readability.

Author: gn00295120

src/agents/extensions/models/litellm_model.py

@@ -369,7 +369,8 @@ async def _fetch_response(
             return ret
 
         # Convert tool_choice to the correct type for Response
-        # tool_choice can be a Literal, ToolChoiceFunction, dict from ChatCompletions Converter, or omit
+        # tool_choice can be a Literal, ToolChoiceFunction, 
+        # dict from ChatCompletions Converter, or omit
         response_tool_choice: Literal["auto", "required", "none"] | ToolChoiceFunction
         if tool_choice is omit:
             response_tool_choice = "auto"