chore(docs): update `migrating-to-v5.mdx` copy

[chriseling]

Updating docs to clarify based on speedbumps I encountered during the migration process. Please check for correctness.

☕️ Reasoning

🧢 Checklist

• [ ] Documentation
• [ ] Tests
• [ ] Ready to be merged

🎫 Affected issues

📌 Resources

• Security guidelines
• Contributing guidelines
• Code of conduct
• Contributing to Open Source

[vercel[bot]]

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Name	Status	Preview	Comments	Updated (UTC)
auth-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 6, 2024 6:56pm

1 Ignored Deployment

| Name | Status | Preview | Comments | Updated (UTC) | | :--- | :----- | :------ | :------- | :------ | | **next-auth-docs** | ⬜️ Ignored ([Inspect](https://vercel.com/authjs/next-auth-docs/G5QwRycpdFdXZcZ2jWdcWQvK3HWx)) | [Visit Preview](https://next-auth-docs-git-fork-chriseling-chriseling-patch-1-authjs.vercel.app) | | May 6, 2024 6:56pm |

[vercel[bot]]

@chriseling is attempting to deploy a commit to the authjs Team on Vercel.

A member of the Team first needs to authorize it.

[chriseling]

Fixed lint and formatting

[github-actions[bot]]

Broken Link Checker

1 broken links found. Links organised below by source page, or page where they were found.

1) /getting-started/session-management/protecting

Target Link	Link Text
/getting-started/session-management/protecting&framework=express	"the examples above"