core: Clean up includes

Follow up for 836e4e7ea8

src/core/manager.c

@@ -9,6 +9,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include "sd-bus.h"
 #include "sd-daemon.h"
 #include "sd-messages.h"
 #include "sd-path.h"
@@ -51,9 +52,7 @@
 #include "install.h"
 #include "io-util.h"
 #include "iovec-util.h"
-#include "label-util.h"
 #include "libaudit-util.h"
-#include "load-fragment.h"
 #include "locale-setup.h"
 #include "log.h"
 #include "manager-dump.h"