Do not call HTMLParser.unescape() in Python 3.9 in six

[radarhere]

Presumably, #11419 will be resolved at some point in the future by upgrading the base image to Python > 3.8. Maybe by #11420, maybe by #12027, maybe by a PR that has yet to be created.

When that happens, 'six' will have a problem.

oss-fuzz/projects/six/fuzz_six.py

Lines 58 to 59 in 7fa4a40

	six.moves.html_parser.HTMLParser().unescape(
	fdp.ConsumeUnicodeNoSurrogates(fdp.ConsumeIntInRange(1, 1024)))

In Python 3.9, 'unescape' was removed from HTMLParser - https://docs.python.org/3/whatsnew/3.9.html#porting-to-python-3-9

The unescape() method in the html.parser.HTMLParser class has been removed (it was deprecated since Python 3.4).

Looking at the 'six' source code, unescape isn't actually called by anything internally. HTMLParser is sure, but that's it. So if the method is gone in Python >= 3.9, then there's no need to continue testing it when Python is upgraded.

[github-actions]

radarhere is a new contributor to projects/six. The PR must be approved by known contributors before it can be merged.