fix: ensure comma is also pruned if necessary

[dummdidumm]

immediately after merging #14006 I noticed there's a bug when pruning one selector in a list of several; this fixes it

no changeset because not released yet

[changeset-bot]

⚠️ No Changeset found

Latest commit: 10c25c0

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[pkg-pr-new]

pnpm add https://pkg.pr.new/svelte@14032

commit: 10c25c0