block: stop setting the nomerges flags in blk_cleanup_queue

These flags only apply to file system I/O, and all file system I/O is
already drained by del_gendisk and thus can't be in progress when
blk_cleanup_queue is called.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20220619060552.1850436-5-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>