wrong `prev` offset

[vincentsarago]

https://github.com/developmentseed/tipg/blob/3a7ed4ffc9f4fe9acd0d660dacd73eeda3ff89d1/tipg/collections.py#L791-L796

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"
}