tree-wide: drop locale.h when locale-util.h is included

src/systemctl/systemctl.c

@@ -3,7 +3,6 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
-#include <locale.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdio.h>