fix: remove deprecated schema and use model_json_schema instead in ll…

…m_interface

src/planai/llm_interface.py

@@ -325,7 +325,7 @@ def get_format_instructions(pydantic_object: Type[BaseModel]) -> str:
 {schema}
 ```
 """
-        schema = pydantic_object.schema().copy()
+        schema = pydantic_object.model_json_schema().copy()
 
         schema.pop("title", None)
         schema.pop("type", None)