fix Custom formatters not working with modifiers

[andrewgsavage]

• Closes Custom formatters not working with modifiers (Undocumented breaking change in 0.24) #2017
• 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 #2021 will not alter performance

_{Comparing andrewgsavage:format (17e055a) with master (2493241)}

Summary

✅ 437 untouched benchmarks