python: drop explicit output_encoding='utf-8' in mako templates

Python 3 handles unicode strings by default, so we can drop all that.

Suggested-by: Dylan Baker <dylan@pnwbakers.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3674>

src/util/driconf_static.py

@@ -223,6 +223,6 @@ static const struct driconf_device *driconf[] = {
 xml = sys.argv[1]
 dst = sys.argv[2]
 
-with open(dst, 'wb') as f:
-    f.write(Template(template, output_encoding='utf-8').render(driconf=DriConf(xml)))
+with open(dst, 'w') as f:
+    f.write(Template(template).render(driconf=DriConf(xml)))