try
$ yay -Ss protonup
aur/protonup-ng-git 0.1.4.r2.gf60ee76-1 (+2 1.05)
Install and Update Proton-GE, a version for the new naming convention
aur/protonup-git 0.1.4.r2.gf60ee76-1 (+5 0.22)
Install and Update Proton-GE
aur/protonup-qt 2.7.4-1 (+20 5.85)
Install and manage Proton-GE and Luxtorpeda for Steam and Wine-GE for Lutris
The package you are normally using for protonup is protonup-qt, as @ricklinux already mentioned.
Therefor your syntax should be:
sudo pacman -R protonup-qt
Edit: Should you have taken one of the others then you have to adjust it of course. @ricklinux has listed them all so you can just copy them to try them out