fs: remove an outdated comment on mpage_writepages

fs: remove an outdated comment on mpage_writepages

Patch series "remove generic_writepages"

This series removes generic_writepages by open coding the current
functionality in the three remaining callers.  Besides removing some
code the main benefit is that one of the few remaining ->writepage
callers from outside the core page cache code go away.

This patch (of 6):

mpage_writepages doesn't do any of the page locking itself, so remove and
outdated comment on the locking pattern there.

Link: https://lkml.kernel.org/r/20221229161031.391878-1-hch@lst.de
Link: https://lkml.kernel.org/r/20221229161031.391878-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>