nspawn: '-C' option has been removed

Fixup for 9444b1f "logind: add infrastructure to keep track of
machines, and move to slices."

src/nspawn/nspawn.c

@@ -175,7 +175,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "+hD:u:C:bM:jS:", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "+hD:u:bM:jS:", options, NULL)) >= 0) {
 
                 switch (c) {