Update Next versions to latest 14 and 15

[vicb]

---

This is part 1 of 2 in a stack made with GitButler:

•  2  fix: patch the webpack runtime when there is a single chunk #452
•  1  Update Next versions to latest 14 and 15 #451 👈

[changeset-bot]

⚠️ No Changeset found

Latest commit: 2a6b571

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.

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[pkg-pr-new]

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pnpm add https://pkg.pr.new/@opennextjs/cloudflare@451

commit: 2a6b571

[vicb]

Thanks for the reviews