nilfs2: remove calls to folio_set_error() and folio_clear_error()

Nobody checks this flag on nilfs2 folios, stop setting and clearing it. 
That lets us simplify nilfs_end_folio_io() slightly.

Link: https://lkml.kernel.org/r/20240420025029.2166544-17-willy@infradead.org
Link: https://lkml.kernel.org/r/20240430050901.3239-1-konishi.ryusuke@gmail.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>