It all depends on who did it and when. Tours shot prior to a certain date should be in your own GBP account so you can control and remove them. Tours photographed by other photographers will be under their control and you will need to request with them to get the old tour removed. Unfortunately it is not an exact science and if the photographer has left the program or is not cooperative that is their remit and your next recourse would be to make contact with Google to get the out of date imagery removed.