Fix py38 type hint

Author: Ale-Cas

pydantic_extra_types/mongo_object_id.py

@@ -43,7 +43,7 @@ class MongoDocument(BaseModel):
     OBJECT_ID_LENGTH = 24
 
     @classmethod
-    def __get_pydantic_core_schema__(cls, source: type[Any], handler: GetCoreSchemaHandler) -> core_schema.CoreSchema:
+    def __get_pydantic_core_schema__(cls, source: Any, handler: GetCoreSchemaHandler) -> core_schema.CoreSchema:
         return core_schema.json_or_python_schema(
             json_schema=core_schema.str_schema(min_length=cls.OBJECT_ID_LENGTH, max_length=cls.OBJECT_ID_LENGTH),
             python_schema=core_schema.union_schema(