Fix broken doc links for App namespaces

[CamWass]

This PR updates broken documentation links for App namespaces. The old links had an outdated anchor and didn't take the user to the relevant heading.
Old link:
https://kit.svelte.dev/docs/types#the-app-namespace
New link:
https://kit.svelte.dev/docs/types#app

Note:

Some tests failed for both HEAD and my patch. Since I only modified comments, I decided to open the PR anyway to see what the CI has to say.

---

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🦋 Changeset detected

Latest commit: 4cc9db1

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

This PR includes changesets to release 1 package

Name	Type
create-svelte	Patch

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