Make use_texture_alpha an mobs_mc.entity setting

mods/ENTITIES/mcl_mobs/api.lua

@@ -3712,7 +3712,7 @@ end
 
 minetest.register_entity(name, {
 
-	use_texture_alpha = true,
+	use_texture_alpha = def.use_texture_alpha,
 	stepheight = def.stepheight or 0.6,
 	name = name,
 	type = def.type,

mods/ENTITIES/mobs_mc/slime+magma_cube.lua

@@ -110,6 +110,7 @@ local slime_big = {
 	spawn_small_alternative = "mobs_mc:slime_small",
 	on_die = spawn_children_on_die("mobs_mc:slime_small", 4, 1.0, 1.5),
 	fire_resistant = true,
+	use_texture_alpha = true,
 }
 mobs:register_mob("mobs_mc:slime_big", slime_big)