fix the doctypes lint

Author: tabatkins

.github/workflows/lint/lint-doctypes.py

@@ -1,11 +1,7 @@
 from __future__ import annotations
 
-import os
-import sys
-import typing
-
 import kdl
 
-with io.open("boilerplate/doctypes.kdl", "r") as fh:
+with open("boilerplate/doctypes.kdl", "r") as fh:
 	text = fh.read()
 	kdl.parse(text)