Simplify workflow docs

[deliahu]

• Consider bringing back info for when you should use a batch api vs realtime api (it could be a single page, it used to be two pages) (David mentioned)
• Consider bringing back compute? (it's not documented and not necessarily obvious how to specify memory) (also, the error message links to docs.cortex.dev, but there is currently no info in our docs about this; grep some valid examples are (David mentioned)