kernfs: remove outdated and confusing comment

Grabbing the parent is not happening anymore since 2010 (e72ceb8c
"sysfs: Remove sysfs_get/put_active_two"). Remove this confusing
comment.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/file.c

@@ -785,7 +785,6 @@ static unsigned int kernfs_fop_poll(struct file *filp, poll_table *wait)
 	struct kernfs_node *kn = filp->f_path.dentry->d_fsdata;
 	struct kernfs_open_node *on = kn->attr.open;
 
-	/* need parent for the kobj, grab both */
 	if (!kernfs_get_active(kn))
 		goto trigger;