nilfs2: remove wbc->for_reclaim handling

nilfs2: remove wbc->for_reclaim handling

Since commit 013a07052a1a ("nilfs2: convert metadata aops from writepage
to writepages"), nilfs_mdt_write_folio can't be called from reclaim
context any more.  Remove the code keyed of the wbc->for_reclaim flag,
which is now only set for writing out swap or shmem pages inside the swap
code, but never passed to file systems.

Link: https://lkml.kernel.org/r/20250508054938.15894-7-hch@lst.de
Link: https://lkml.kernel.org/r/20250516123417.6779-1-konishi.ryusuke@gmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>