Change field_is_complex to be more similar to pydantic v1

pydantic_settings/sources.py

@@ -64,7 +64,7 @@ def field_is_complex(self, field: FieldInfo) -> bool:
             bool: Whether the field is complex.
         """
         result = _annotation_is_complex(field.annotation)
-        print(result)
+        print(result, field.annotation)
         return result
 
     def prepare_field_value(self, field_name: str, field: FieldInfo, value: Any, value_is_complex: bool) -> Any:
@@ -446,8 +446,6 @@ def find_case_path(dir_path: Path, file_name: str, case_sensitive: bool) -> Opti
 
 def _annotation_is_complex(annotation: type[Any] | None) -> bool:
     origin = get_origin(annotation)
-    if origin_is_union(origin):
-        return all(_annotation_is_complex(arg) for arg in get_args(annotation))
     return (
         _annotation_is_complex_inner(annotation)
         or _annotation_is_complex_inner(origin)