docs: clean up tutorials

[sathvikbhagavan]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[sathvikbhagavan]

@ChrisRackauckas, I think this can be merged now. After this, I feel for a few examples, surrogates perform very poorly. Need to investigate why.