Doors: Trim open fence gate collision box

Previously, the collision box extended into an empty node, causing
falling node objects to land on the open gate but not transform
back into normal nodes. Now fallng node objects will fall through and
either side of the end of the open gate and transform back.

mods/doors/init.lua

@@ -706,7 +706,7 @@ function doors.register_fencegate(name, def)
 	fence_open.collision_box = {
 		type = "fixed",
 		fixed = {{-1/2, -1/2, -1/4, -3/8, 1/2, 1/4},
-			{-5/8, -3/8, -14/16, -3/8, 3/8, 0}},
+			{-5/8, -3/8, -1/2, -3/8, 3/8, 0}},
 	}
 
 	minetest.register_node(":" .. name .. "_closed", fence_closed)