Update README.md to reflect new dolthub "About / Data Sources" page

[DouglasKrouth]

Previous README had a link provided in "What data are we scraping?" subsection that pointed to a dead-end on do1thub (https://www.dolthub.com/repositories/pdap/datasets/query/master?q=SELECT+*%0AFROM+%60datasets%60%0Awhere+status_id+%3D+1%0A%0A&active=Tables).

Not sure if the new link I added was exactly where we want this link to point to, currently modified it to point it at the dolthub base data_sources page.

[josh-chamberlain]

@DouglasKrouth we're in the midst of fixing stuff like this in the scraper cleanup pr, one of my commits on it removes the line you're fixing. @thejqs is currently working on that. I appreciate you making the fix, though!

[thejqs]

I came here to say what Josh already said. Hooray for teamwork.

[DouglasKrouth]

Awesome. Thanks for the fast review, didn't mean to cause any rework :)