Y = normalToricVariety X
If $X$ is a GKM variety that was originally constructed using normalToricVariety, then this method reverts $X$ to a NormalToricVariety.
i1 : X = toricProjectiveSpace 2;
i2 : Y = makeGKMVariety X o2 = a "GKM variety" with an action of a 2-dimensional torus o2 : GKMVariety
i3 : assert(normalToricVariety Y === X)