OL: Decrease the tapping distance to 13um

- even 14um didn't work in some cases and the claimed fix at
https://github.com/The-OpenROAD-Project/OpenROAD/issues/562 still doesn't do
it, so until we debug and sort it out, we're gonna tap slightly more
often...

sky130/openlane/config.tcl

diff --git a/sky130/openlane/config.tcl b/sky130/openlane/config.tcl
index c80e203..f26d033 100755
--- a/sky130/openlane/config.tcl
+++ b/sky130/openlane/config.tcl
@@ -67,7 +67,7 @@
 
 set ::env(CTS_SQR_CAP) 0.258e-3
 set ::env(CTS_SQR_RES) 0.125
-set ::env(FP_TAPCELL_DIST) 14
+set ::env(FP_TAPCELL_DIST) 13
 
 # Tracks info
 set ::env(TRACKS_INFO_FILE) "$::env(PDK_ROOT)/$::env(PDK)/libs.tech/openlane/$::env(STD_CELL_LIBRARY)/tracks.info"