userns: Kill bogus declaration of function release_uids

There is no release_uids function remove the declaration from sched.h
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>

include/linux/sched.h

@@ -2184,7 +2184,6 @@ static inline struct user_struct *get_uid(struct user_struct *u)
 	return u;
 }
 extern void free_uid(struct user_struct *);
-extern void release_uids(struct user_namespace *ns);
 
 #include <asm/current.h>