Include a space after "syncterm" and before arguments.

Fix issue reported WitNik (BGGRSCYN) on DOVE-Net:
```
sbbs@raspberrypi:~ $ /sbbs/exec/umonitor -iC
...
sh: 1: /sbbs/exec/syncterm-iC: not found
```

src/sbbs3/umonitor/umonitor.c

@@ -1148,7 +1148,7 @@ USAGE:
 						do_cmd(str);
 						break;
 					case 3:
-						sprintf(str,"%ssyncterm",cfg.exec_dir);
+						sprintf(str,"%ssyncterm ",cfg.exec_dir);
 						for(j=1; j<argc; j++) {
 							strcat(str,"'");
 							strcat(str,argv[j]);