Update Groq URI base

[walshhub]

All Submissions:

• [x] Have you followed the guidelines in our Contributing document?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] Have you added an explanation of what your changes do and why you'd like us to include them?

Update the README to include a more accurate Groq URI base

[alexrudall]

Thanks @walshhub!