Documentation: don't remove lock manager fl_release_private

I thought I'd removed the last user of this, but missed
fs/locks.c:lease_release_private_callback().  Thanks to Christoph for
pointing this out.
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

Documentation/filesystems/Locking

@@ -327,12 +327,14 @@ fl_release_private:	yes	yes
 prototypes:
 	int (*fl_compare_owner)(struct file_lock *, struct file_lock *);
 	void (*fl_notify)(struct file_lock *);  /* unblock callback */
+	void (*fl_release_private)(struct file_lock *);
 	void (*fl_break)(struct file_lock *); /* break_lease callback */
 
 locking rules:
 			BKL	may block
 fl_compare_owner:	yes	no
 fl_notify:		yes	no
+fl_release_private:	yes	yes
 fl_break:		yes	no
 
 	Currently only NFSD and NLM provide instances of this class. None of the