Remove broken PlayCanvas React example cards

[abstrakt8]

Summary

• So there are three examples that still point to the deprecated Vercel page.
• I had to search through the git history to revive these old examples, but none of them worked fine as easily as I had hoped. They are setup using some shared components and are not just self-contained isolated examples that we could easily copy over.
• I could revive the Physics example, but need to revive the other ones as a follow up. Am thinking of using a PlayCanvas logo instead of the skull.sog for the Gaussian Splatting example.

Testing

• npm run start