Delete btor.ys

.ys script not needed

backends/btor/btor.ys

@@ -1,18 +0,0 @@
-proc; 
-opt; opt_const -mux_undef; opt;
-rename -hide;;;
-#converting pmux to mux
-techmap -share_map pmux2mux.v;;
-#explicit type conversion
-splice; opt;
-#extracting memories;
-memory_dff -wr_only; memory_collect;;
-#flatten design
-flatten;;
-#converting asyn memory write to syn memory
-memory_unpack; 
-#cell output to be a single wire
-splitnets -driver;
-setundef -zero -undriven;
-opt;;;
-