fix(remix-react): dedupe links in getStylesheetPrefetchLinks

[grinkus-adapt]

Closes: #5677

• Docs
• Tests

Deduplicating links in getStylesheetPrefetchLinks avoids inserting links with the same key prop, which React dev complains about. It's not an issue in prod build, but this tweak makes the developer experience a bit better in an edge-case where there's a stylesheet that's imported in the sub-page that a Link with prefetch prop is pointing to.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 24f9d13

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

This PR includes changesets to release 18 packages

Name	Type
@remix-run/react	Patch
@remix-run/testing	Patch
create-remix	Patch
remix	Patch
@remix-run/architect	Patch
@remix-run/cloudflare	Patch
@remix-run/cloudflare-pages	Patch
@remix-run/cloudflare-workers	Patch
@remix-run/css-bundle	Patch
@remix-run/deno	Patch
@remix-run/dev	Patch
@remix-run/eslint-config	Patch
@remix-run/express	Patch
@remix-run/netlify	Patch
@remix-run/node	Patch
@remix-run/serve	Patch
@remix-run/server-runtime	Patch
@remix-run/vercel	Patch

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[markdalgleish]

Thanks for the PR! As mentioned in the original issue, I've opened a PR that goes a bit further than your suggested fix because this was actually a symptom of a deeper issue, so I'm closing this in favour of this one: #7060.