fix: support pytest on python 3.12 wrt Fraction formatting change

[mtasaka]

python 3.12 supports float-style formatting for Fraction by python/cpython#100161 .
With this change, when ":n" format specifier is used in format() for Fraction type, this now raises ValueError instead of previous TypeError.

To make pytest succeed with python 3.12, make
pint.testing.assert_allclose also rescue ValueError .

Fixes #1818 .

• Executed pre-commit run --all-files with no errors
• The change is fully covered by automated unit tests
• Documented in docs/ as appropriate
• Added an entry to the CHANGES file

[codspeed-hq]

CodSpeed Performance Report

Merging #1821 will not alter performance

_{Comparing mtasaka:py312-pytest-fix (2bd6677) with master (4cca8ab)}

Summary

✅ 421 untouched benchmarks

[hgrecco]

Awesome! Thanks a lot.