This reverts commit 253c2282917ecade5b8356d592edab40b1d517f5.
Apparently this warning is full of crap. Explicitly
setting use_texture_alpha in the node def does
something DIFFERENT than what the engine says
it's doing enabling it internally. use_texture_alpha
enables alpha BLENDING, which is what we
don't want with interpolation filters, whereas
leaving it off enables alpha THRESHOLDING which
is exactly what we want.
1632b6352a