Fixup description of default values for fixture-parentheses and mark-parentheses

[AlexWaygood]

I noticed while creating a PR to update the schemastore entry for Ruff that there was still some language here that implied that these defaulted to true; but they default to false on ruff 0.6+. #12838 changed some but not all the language here.

[codspeed-hq]

CodSpeed Performance Report

Merging #12904 will improve performances by 10.63%

_{Comparing pt-default (408301a) with main (b9da316)}

Summary

⚡ 1 improvements
✅ 31 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	pt-default	Change
⚡	linter/all-with-preview-rules[numpy/globals.py]	911.3 µs	823.7 µs	+10.63%

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[MichaReiser]

Thanks