This will serve no purpose other than to alienate you from their program.
You’re basically telling them that you already got in somewhere, which will more likely make them think “Well, this person already got in somewhere else, so we can open up a spot for another candidate in need“ rather than the effect I think you’re going for / what you’re hoping they’ll be thinking (i.e., “Oh no they got in somewhere they must be really awesome we have to accept OP now”).
Do NOT mention any other acceptances unless explicitly asked. Saying anything without prompting will look very unprofessional. If it is brought up, tell them you are fortunate to hold acceptances at another school but that you would choose their school over the aforementioned because X, Y, and Z.