I would reduce the pellets slowly as you start feeding fruits and veggies to about a 1/4 per every 5 lbs. Pellets have many minerals and vitamins they still need so I would still feed in small amounts. It is possible to not provide pellets, but you would need to do a lot of research to make sure your rabbit gets the right nutrition. I have noticed as my bunnies get older, I'm constantly having to make small adjustments here and there and each rabbits diet is a little different.
For example, out of my bunch 3/4 can't eat curly kale, 2/4 can't eat dino kale, but 4/4 can get red russian. I keep a long spreadsheet with all the details and date of when/why I've had to make the changes and what not. Start small and pay attention to their stool about an hour after they eat and make sure to look out of gas. It's pretty common for new stuff to give bunnies gas and gas can get really uncomfortable for bunnies so be careful.