wrong `prev` offset

[vincentsarago]

tipg/tipg/collections.py

Lines 791 to 796 in 3a7ed4f

	return ItemList(
	items=features,
	matched=matched,
	next=offset + returned if matched - returned > offset else None,
	prev=max(offset - returned, 0) if offset else None,
	)

curl https://vector.eoapi.dev/collections/public.countries/items\?limit\=100\&offset\=200 | jq '.links[2]'
{
  "href": "https://vector.eoapi.dev/collections/public.countries/items?limit=100&offset=159",
  "rel": "prev",
  "type": "application/geo+json",
  "title": "Previous page"
}