To remove products from your Wix store, you must delete the product from your Wix store directly.
After the deletion in Wix, click on 'Sync products' button located on the top right corner of the store page in Gelato. The removed product will no longer be listed on the page after syncing products.
This applies to both products added from Gelato to your Wix store, as well as products added from Wix that were connected to Gelato.