"Would you peel off (pull off) the sticker which is on the computer, as I am holding the monitor with my hands.""Ripping off" has two meanings. The one that applies here is to remove it very forcefully and quickly, the way one removes an adhesive bandage from skin in order to reduce the time during which one feels pain.
The sticker was probably not removed that way. It probably wore off, or perhaps was torn off, but there would be no need for force or speed. I'd say "torn off" if you know that it was removed that way. Otherwise, I'd say "worn off," if it came off as the result of using the computer over time, or just "the sticker isn't there any more."
(The second meaning of "rip off" has to do with cheating someone.)