docs: remove h4 headers

[sacrosanctic]

related to sveltejs/svelte.dev#2064

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
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• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.
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Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

⚠️ No Changeset found

Latest commit: a6752b0

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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[pkg-svelte-dev]

Install the latest version of svelte from a6752b0:

pnpm add https://pkg.svelte.dev/svelte/c/a6752b0e297bb63020bd42aa56d5d13649254ef9

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/svelte/pr/18502

Note

This PR is from a fork. A maintainer must approve approve each commit before it can be built and installed.