[sky130_mux] metal paths collide for unfortunately-sized transistors

[growly]

logic does not consider spacing between lower and upper left mux arms when running metal1, since it now runs into the output of the left output mux (centre-pic, left). easy option would be to space out the quadrants, though that would lengthen wires. in this case there is space beneath the output mux (left) but that might not be true always