When you place down the light block, you cannot remove it by holding it with a light block as the recent Java snapshot has. You have to manually remove it by placing another block in the light block to get rid of the light it emits.
Step to Reproduce
1. Place down light blocks (you obtain it by /give commands)
2. Try to remove it while holding the light block.
---> ❌ You can't.
Confirmed)