[issue41919] Modify test_codecs to use the new codecs.unregister() function

[hai shi]

hai shi <shihai1991 at 126.com> added the comment:

> AS this is masking other issues in the build bots, we need to revert the commit unless is fixed in 24 hours per the buildbot workflow

Thanks, Pablo. I checked that only test_io.py have resource leak.
I create PR-22973, pls take a look if you have free time, thanks.

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<https://bugs.python.org/issue41919>
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