Why does my iPhone SE 3 have two QR code scanners in Control Center?

The QR Code Control does fall into two categories, but they are the exact same control. As Phil0124 states, you likely have accidentally added a second one and you can simply remove it by tapping the + in the top left Control Center, then just tapping - on top of one of the widgets to remove.

Probably, you added a second one? You can add multiple controls for the same thing.

Just remove one of them.

Click here ➡️ Use and customize Control Center on iPhone - Apple Support