How to remove unknown part display

If your display is truly the original that came with your iPhone, the message could be an indication that your display has malfunctioned and needs service or replacement. You'll need to take it to an Apple Store or authorized service center, or send it to Apple, for evaluation.

See Apple Repair and Repair Status Check - Official Apple Support

Did you have the screen replaced on your iPhone anywhere other than an Apple Store or an actual Apple Authorized Service Provider? If you did, you don't have an authentic screen and you can't remove the message.