feat: update /concepts/nodes page

[SgtPooki]

• feat: update /concepts/nodes page

Describe your changes

• Removes mentions of js-ipfs in concepts/nodes page
• Removes mentions of preload nodes, since they're going away [Tracking Issue] Shutdown PL-hosted delegated and preload nodes ipfs#499
• Updates some older mentions and clarifies some language
• Uses TODO_JS_IPFS_DEPRECATION in places that STILL NEED WORK.

Files changed

• docs/concepts/nodes.md

What issue(s) does this address?

Part of #1611

Does this update depend on any other PRs?

• Cleanup js-ipfs mentions #1620

Checklist before requesting a review

• Passing the beta version of the Check Markdown links for modified files check. Action results can be viewed here.

Checklist before merging

• Passing all required checks (The beta Check Markdown links for modified files check is not required)

[ElPaisano]

@SgtPooki are there any other changes you'd like to make before I merge this into https://github.com/ipfs/ipfs-docs/tree/js-ipfs-cleanup for final cleanup and merging?

[SgtPooki]

@SgtPooki are there any other changes you'd like to make before I merge this into https://github.com/ipfs/ipfs-docs/tree/js-ipfs-cleanup for final cleanup and merging?

Theres a few items left. Let me handle those and update you. Gimme a few

[SgtPooki]

@ElPaisano seems like we should be ready to go now. It was only the relay v1 task that was left.