The boulders are not a glitch and will not be removed.
Before complaining about boulders, think that 3 weeks ago there were no ranches.
Nothing is perfect, and the boulders are randomly placed on the ranches, to make ranches more real and different at the same time.
I know it is frustrating not to be able to demolish them, but look at the bright side.. Boulders take only around 5% of the ranch space.