filesystems/locking: fix Malformed table warning

Update the bottom border to be the same as the top border.

Documentation/filesystems/locking.rst:274: WARNING: Malformed table.
Bottom/header table border does not match top border.

Fixes: 730633f0 ("mm: Protect operations adding pages to page cache with invalidate_lock")
Link: https://lore.kernel.org/r/20210727232212.12510-1-rdunlap@infradead.org


Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>