Remove deprecated Node SDK references

[wobsoriano]

Important

🔎 Previews:

• https://clerk.com/docs/pr/1880#explore-by-backend-framework (new item)
• https://clerk.com/docs/pr/1880/quickstarts/overview#backend (new item)
• https://clerk.com/docs/pr/1880/references/backend/sessions/get-token#examples-with-frameworks (replaced Node examples with Express)
• https://clerk.com/docs/pr/1880/users/creating-users (replaced Node examples with Express)
• https://clerk.com/docs/pr/1880/users/deleting-users (replaced Node examples with Express)
• https://clerk.com/docs/pr/1880/references/backend/types/auth-object#use-get-token-in-the-backend (replaced Node examples with Express)
• https://clerk.com/docs/pr/1880/users/user-impersonation#detect-impersonated-sessions-in-the-backend (replaced Node examples with Express)
• https://clerk.com/docs/pr/1880/users/metadata (replaced Node examples with Express)
• Removed in sidebar SDK references

⚠️ Redirects: https://github.com/clerk/clerk/pull/947

Explanation:

• As of January 10, 2025, we have completed the deprecation period for @clerk/clerk-sdk-node (see changelog)
• We need to update our docs to reflect this change and guide users to the current recommended SDKs

This PR:

• Removes all references to the deprecated @clerk/clerk-sdk-node package
• Updates Node.js integration examples to use @clerk/express

Checklist

• I have clicked on "Files changed" and performed a thorough self-review
• I have added the "deploy-preview" label and added the preview link(s) to this PR description
• All existing checks pass

[github-actions]

Hey, here’s your docs preview: https://clerk.com/docs/pr/1880

[LekoArts]

There's a TODO in https://github.com/clerk/clerk-docs/blob/main/docs/references/express/overview.mdx in case we want to go through with that

[alexisintech]

Looks good to merge!

Redirects are here: https://github.com/clerk/clerk/pull/947