breaking: remove Node polyfills

[teemingc]

closes #15258

This PR removes the export @sveltejs/kit/node/polyfills and the shims from the node and netlify adapter. They were only needed while we still supported Node 18

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🦋 Changeset detected

Latest commit: e699bdc

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

This PR includes changesets to release 1 package

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@sveltejs/kit	Major

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15430-svelte.vercel.app/

[teemingc]

The docs are failing to build because https://svelte.dev/docs/kit/modules links to the now non-existent Node polyfill docs. We'll need to remove that reference sveltejs/svelte.dev#1820