To remove products added from Gelato to your store, you first need to delete the product in Woocommerce and then sync products on Gelato's side.
Go to Woocommerce dashboard section 'Products'→'All products' and click on the 'Bin' button
Then, from the Stores section, select your store and click on 'Sync products' button located on the top right corner of the page. The removed product will no longer be listed after syncing products.