If you want to disable it completely, you can go to:
Settings → Configure Krita → Canvas Input Settings → Show Popup Widget
There you will see the defined activation control for it:
Where it says ‘Mouse Button’, do a right-click on there and you will get the ‘Delete Shortcut’ button that you can press to delete the setting.
After that, you’ll never see the popup palette again.
You also won’t see contect menus for the other tools either.
So, it would be better to stop your tablet from doing this.