FIX: intake-esgf + rooki notebook

[nocollier]

This PR is needed as the WPS address in there now is not functional. While I was at it, I took a pass and cleaned up some things I found as well:

• Zach has changed the endpoint to something that looks more consistent
• Removed a redundant cat = ESGFCatalog()
• Added data_node = "esgf-node.ornl.gov" to the search. ORNL has info about holdings elsewhere so it is actually needed to make sure we don't try to load data that isn't at ORNL
• Renamed the dataset_id to a rooki_id, dataset_id is something else in ESGF parlance and I thought it wise to avoid confusion
• The rooki function didn't use the argument, it just used the first id, i.e. dataset_ids[0]
• Expanded the explanation in several places

[github-actions]

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[nocollier]

@mgrover1 I couldn't check the preview as it was returning 404 but it renders locally for me.

[mgrover1]

This looks great - let's merge and see what it renders like on the main branch