Add disclaimer in Graphics Kexts about NootedRed not being supported in the installer

Opencore Install Guide
https://dortania.github.io/OpenCore-Install-Guide/ktext.html#graphics

In the Graphics section where it says to use WhateverGreen, I think there should be a disclaimer saying that even when using an AMD iGPU and planning to use NootedRed, the installer does not support NootedRed and you should use WhateverGreen until you get MacOS installed and then change to NootedRed. I spent a lot of time and happened to find one tiny article that said that, and as soon as I swapped NootedRed with WhateverGreen my problem was fixed.