[fix] adapter-netlify: return the right headers

[JeanJPNM]

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While looking at possible causes for #1911 I found a logical error inside the entry of adapter-netlify, it was returing the request headers instead of the response headers.

Idk if this should have a changelog.

[changeset-bot]

🦋 Changeset detected

Latest commit: 6f5695a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/adapter-netlify	Patch

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