remove unused includes

This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.

src/resolve/resolved.c

@@ -22,7 +22,6 @@
 #include "sd-event.h"
 #include "sd-daemon.h"
 #include "mkdir.h"
-#include "label.h"
 #include "capability.h"
 #include "selinux-util.h"