update nangate45/ariane136 place density and metrics

Signed-off-by: Augusto Berndt <[email protected]>

Author: gudeh

flow/designs/nangate45/ariane136/config.mk

@@ -28,3 +28,4 @@ export PLACE_PINS_ARGS = -exclude left:0-500 -exclude left:1000-1500: -exclude r
 export MACRO_PLACE_HALO = 10 10
 export MACRO_PLACE_CHANNEL = 20 20
 export TNS_END_PERCENT = 100
+export PLACE_DENSITY = 0.35