This commit fixes a test failure for `extmod/re_sub.py` where the code,
whilst being correct, would not make the test pass due to a newer
Python version than expected.
On Python 3.13, running `tests/extmod/re_sub.py` would yield a
deprecation warning about `re.sub` not providing the match count as a
keyword parameter. This warning would be embedded in the expected test
result and thus the test would always fail.
Co-authored-by: stijn <stijn@ignitron.net>
Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
