verilog_backend: Do not run bwmuxmap even if in expr mode

While bwmuxmap generates equivalent logic, it doesn't propagate x bits
in the same way, which can be relevant when writing verilog.

backends/verilog/verilog_backend.cc

@@ -2329,7 +2329,6 @@ struct VerilogBackend : public Backend {
 		if (!noexpr) {
 			Pass::call(design, "bmuxmap");
 			Pass::call(design, "demuxmap");
-			Pass::call(design, "bwmuxmap");
 		}
 		Pass::call(design, "clean_zerowidth");
 		log_pop();