Modified the FOM generation to make the fill density of FOM fill
closer to 45% (about 10% below the maximum allowed density).

sky130/magic/sky130.tech

diff --git a/sky130/magic/sky130.tech b/sky130/magic/sky130.tech
index e68cad4..f0683f4 100644
--- a/sky130/magic/sky130.tech
+++ b/sky130/magic/sky130.tech
@@ -1808,7 +1808,7 @@
 # FOM and POLY fill
 #---------------------------------------------------
  templayer	fomfill_pass1 topbox
-        slots   0 4080 1320 0 4080 1320 1360 0
+        slots   0 4080 1600 0 4080 1600 1360 0
         and-not obstruct_fom
 	and	topbox
         shrink  2035