chore: fix dead link

[evan-forbes]

Overview

replaces the dead link with one to the testground repo

Closes #131

Checklist

• [x] New and updated code has appropriate documentation
• [x] New and updated code has new and/or updated testing
• [x] Required CI checks are passing
• [x] Visual proof for any user facing features like CLI or documentation updates
• [x] Linked issues closed with keywords

[Bidon15]

Thanks a lot @evan-forbes !!!