docs: fix links in some errors/warnings

[Rich-Harris]

there's some redundant links in the messages, plus some unnecessarily qualified links

[changeset-bot]

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Latest commit: 4088f8c

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Playground

pnpm add https://pkg.pr.new/svelte@14825

[Rich-Harris]

preview: https://svelte-dev-git-preview-svelte-14825-svelte.vercel.app/

this is an automated message

[Rich-Harris]

will self-merge once green since this is causing noise on docs PRs on svelte.dev (because i mistakenly removed updated links in some generated content)