Disassemble the filler, remove supply line, the escutcheon looks to be caulked in, the supply line is notched to hold the escutcheon flush to the wall. Replace the supply line with a nipple and cap.

Do you know where the shut off valve is?

I don't know how to that that thing off... but I do know they sell caps for pipes in the plumbing department. Some of them glue on, like for the plastic pipes. Some screw on, like some metal pipes. I doubt it's copper, but if it is, there's a way to cap that too. How to make the tile-hole look nice might take more effort, it crosses over two tiles too.

Grade point, we are going to be replacing the tile with a different backsplash

No idea where the shut off valve for that is

If you do not know how to remove the pot filler and do not know how shut off the water, I recommend hiring a licensed plumber.

I do not think you have the resources to DIY.

What does ; grade point” mean mean?

If you are replacing the whole backsplash, then it's moot what the tile hole is then :)

What is below the pot filler? As in the cabinetry below. If you can look in there, see if you can see plumbing pipes in there. Sometimes there will be, sometimes not. If there is, there might be a valve there. If there isn't plumbing there, then it might be coming in from a side or behind rather than below. Or it might go below, but be behind the wall and you need to keep looking for a valve. That takes more tracking down. So check below first and see what's there.