reiserfs: reiserfs.h: delete a duplicated word

Drop the repeated word "than" in a comment.

Link: https://lore.kernel.org/r/20200720001431.29718-1-rdunlap@infradead.org


Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: reiserfs-devel@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>