core[fix]: Fix __dir__ in __init__.py for output_parsers module (#30856)

We have a `list.py` file which causes a namespace conflict with `list`
from stdlib, unfortunately.

`__all__` is already a list, so no need to coerce.

libs/core/langchain_core/output_parsers/__init__.py

@@ -99,4 +99,4 @@ def __getattr__(attr_name: str) -> object:
 
 
 def __dir__() -> list[str]:
-    return list(__all__)
+    return __all__