Short answer
No, that tiny amount of cooked rabbit is fine for cats. It's a safe protein source often used in commercial pet foods. Just keep an eye on your cat for any unusual stomach upset over the next few hours. Call your own vet if you notice vomiting or diarrhea, but that's unlikely from such a small taste.
Rabbit — Food safety facts
Safe to share · Cats · full breakdown on the linked food page
Cooked rabbit is a common novel protein in pet food. Never feed raw wild rabbit.
The full verdict, portion guidance and serving notes are collected on the Rabbit food facts page.