If it’s a Unsafe sticker saying that the device is unsafe then no you shouldn’t take it off and if it’s the Makers Sticker giving you the specs of the power supply then most defiantly leave it on.
As I have no idea what sticker you are refering to I can not help you here with an answer.
Spin with the fan on the power supplies I have seen so it’s not necessary to remove those. The only time you would remove any sticker is if it blocks the outlet of the air flow from a Power Supply so if it’s not blocking a grill leave it in place.