Integrate Bennascar's reshaded boss sprites

[AlexKhayrullin]

Bennascar had contacted me to suggest edits to two boss sprites, and indeed, the added shading on them is an improvement without going too far (he made it a point to only use the colors that are already present on the sprites in question) .

[VectorSatyr]

Note that if these sprites are added to the game, he will need to be credited in some way.