memcg: remove mem_cgroup_uncharge_list()

All users have been converted to mem_cgroup_uncharge_folios() so we can
remove this API.

Link: https://lkml.kernel.org/r/20240227174254.710559-14-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>