mypy error fix

Author: TamiTakamiya

ols/src/llms/providers/registry.py

@@ -12,7 +12,7 @@
 class LLMProvidersRegistry:
     """Registry for LLM providers."""
 
-    llm_providers: ClassVar = {}
+    llm_providers: ClassVar[dict[str, Callable]] = {}
 
     @classmethod
     def register(cls, provider_type: str, llm_provider: Callable) -> None: