fix: apply specificity so that style actually applies to checked radio

[swiing]

:where() has 0 specificity, the consequence of which is that style does not apply, as it is overridden by other css rules. => use :is() instead

Closes #5672

Changed

replace :where() css by :is()

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Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github (Learn more about how to run integration tests)

[joshblack]

Hi there @swiing! 👋 Thanks for taking the time to open up a PR 🙏

When looking at this it seems like the selector has a specificity of 0,1,0 since the :where() is nested within a class. The issue seems to be related to ordering of classes when looking at the compiled CSS:

We could also totally increase the specificity like in this PR (which I think would go to 0,2,0) but I think with how these two interact it would make more sense to change the ordering. I opened up: #5765 to hopefully address this 🤞

Hope that makes sense, let me know if you have any questions!

[swiing]

Hi @joshblack , lgtm