implement `update_until`

It is currently marked as NotImplemented:

Lines 140 to 141 in a92cabf

    
           def update_until(self, time: float) -> None: 
        
               raise NotImplementedError

Since Ribasim currently typically uses adaptive timesteppers, update_until makes more sense to use than update.

Hey @visr this went in with #94

	def update_until(self, time: float) -> None:
	raise NotImplementedError