breaking: remove delta from non-popstate navigations

[teemingc]

This PR addresses a TODO comment to remove the delta property from navigation events which aren't popstate

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🦋 Changeset detected

Latest commit: 9d1290e

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@sveltejs/kit	Major

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15522-svelte.vercel.app/

[elliott-with-the-longest-name-on-github]

lgtm, just a little nit