[connectors] Include isolated Categories in Zendesk article incremental sync

[aubin-tchoi]

Description

This PR fixes an edge case of the article incremental sync.

• Previous behavior: article incremental sync run on brands whose Help Center is selected as a whole.
• Problem: if a user selects single categories, these won't be kept up-to-date.
• Fix: run the incremental sync on brands where at least one category is selected too (overkill but no incremental endpoint for Categories, a permission check is done when syncing the article).

Risk

Low.

Deploy Plan

• Deploy connectors.