Fix 3.9 mypy errors

Author: sanders41

prelude_parser/types.py

@@ -1,6 +1,7 @@
-from __future__ import annotations
+# UP035 and UP006 ignored because Python 3.9 doesn't support the upgrade
 
 from datetime import date, datetime
+from typing import Dict, List, Union  # noqa: UP035
 
-FieldInfo = str | int | float | date | datetime | None
-FlatFormInfo = list[dict[str, FieldInfo]]
+FieldInfo = Union[str, int, float, date, datetime, None]
+FlatFormInfo = List[Dict[str, FieldInfo]]  # noqa: UP006