[python3] utest: utils/test_xmlwriter: Reverted some explicit encoding args.
[python3] utest: utils/test_xmlwriter: Reverted some explicit encoding args.

--HG--
extra : transplant_source : %FE%2BD%B7%00%205%B3%5DV%A9%D1%A1%28%99%E4/G%C4D

userzimmermann/robotframework,userzimmermann/robotframework,userzimmermann/robotframework,userzimmermann/robotframework,userzimmermann/robotframework