fix: remove duplicate get_llm_provider type stub to resolve mypy error

- Remove get_llm_provider from TYPE_CHECKING Protocol class
- Function is already imported from main.py via 'from .main import *'
- Fixes mypy error: Name 'get_llm_provider' already defined (possibly by an import)

litellm/__init__.py

@@ -1507,7 +1507,6 @@ if TYPE_CHECKING:
     get_first_chars_messages: Callable[..., str]
     get_provider_fields: Callable[..., List]
     get_valid_models: Callable[..., list]
-    get_llm_provider: Callable[..., Tuple[str, str, Optional[str], Optional[str]]]
 
     # Response types - truly lazy loaded only (not in main.py or elsewhere)
     ModelResponseListIterator: Type[Any]