Revert additional piston rules.

mesecons_pistons/init.lua

@@ -8,9 +8,7 @@ piston_rules =
  {x=-1, y=1,  z=0},
  {x=-1, y=-1, z=0},
  {x=0,  y=1,  z=1},
- {x=0,  y=-1, z=1},
- {x=0,  y=1,  z=-1},
- {x=0,  y=-1, z=-1}}
+ {x=0,  y=-1, z=1}}
 
 local piston_get_rules = function (node)
 	local rules = piston_rules