Unused pixels in magmacube.png UV texture map & Used section removed in previous fix

The Bug

1. The texture map for the magma cube was cleaned in 23w31a, but a few sections of unused pixels were missed.
2. The bottom face of the model cubes had been removed.

Unused Pixels

unused highlighted in red
used but removed in blue

Fix:

Restores the removed pixels, and removes unused ones