Documentation: xfs: Remove repeated word in comments

Remove the repeated word "the" in comments.

Signed-off-by: Charles Han <hanchunchao@inspur.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>