logind: remove spurious include of <sys/capability.h>

They do not use any functions from libcap directly. The CAP_* constants in use
through these files come from "missing.h" which will import <linux/capability.h>
and complement it with CAP_* constants not defined by the current kernel
headers. The "missing.h" header is imported through "util.h" which gets
imported in "logind.h".

Tested that "systemd-logind" builds cleanly and works after this change.

src/login/logind-dbus.c

@@ -23,7 +23,6 @@
 #include <string.h>
 #include <unistd.h>
 #include <pwd.h>
-#include <sys/capability.h>
 
 #include "sd-id128.h"
 #include "sd-messages.h"

src/login/logind-seat-dbus.c

@@ -21,7 +21,6 @@
 
 #include <errno.h>
 #include <string.h>
-#include <sys/capability.h>
 
 #include "util.h"
 #include "bus-util.h"

src/login/logind-session-dbus.c

@@ -21,7 +21,6 @@
 
 #include <errno.h>
 #include <string.h>
-#include <sys/capability.h>
 
 #include "util.h"
 #include "strv.h"

src/login/logind-user-dbus.c

@@ -21,7 +21,6 @@
 
 #include <errno.h>
 #include <string.h>
-#include <sys/capability.h>
 
 #include "strv.h"
 #include "bus-util.h"