[connectors] fix(Zendesk) - high volumes

[aubin-tchoi]

Description

• Close [Zendesk] Investigate incremental sync high volumes #8969.
• Fix an issue observed in prod and locally where basically all the articles would be resynced at every incremental update.
• The condition to stop the pagination was incorrect.

Response on empty diff:

curl "https://$SUBDOMAIN.zendesk.com/api/v2/help_center/incremental/articles.json?start_time=1732725000" -H "Authorization: Bearer $TOKEN" | jq

{
  "count": 0,
  "next_page": null,
  "end_time": 1,
  "articles": []
}

Risk

Low.

Deploy Plan

• Deploy connectors.