fix: remove empty chunk css imports when using esnext

[matthewp]

Description

Fixes #8330

• When building to esnext a single quote rather than double quote is used. Fixing the regex causes it to remove the empty chunk import statement correctly.

Additional context

This fixes a bug in Astro and Sveltekit (see sveltejs/kit#5052)

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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