ext4: remove incorrect comment for NEXT_ORPHAN()

The comment above NEXT_ORPHAN() was meant for ext4_encrypted_inode(),
which was moved by commit a7550b30

 ("ext4 crypto: migrate into vfs's
crypto engine") but the comment was accidentally left in place.  Since
ext4_encrypted_inode() has now been removed, just remove the comment.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>