A configuration parameter which allows a user to remove a product from the cart by
clicking the data-ajax-cart-quantity-minus button and reaching the “0” value in a
quantity control built using the <ajax-cart-quantity> custom tag.
By default, the minimum value, that a user can reach by clicking a data-ajax-cart-quantity-minus button,
is “1”. Thus, a user can’t remove an item from the cart by this way.
Use the conf method of the liquidAjaxCart object to set
the quantityTagAllowZero to true that lets a user reach the “0” value:
liquidAjaxCart.conf("quantityTagAllowZero", true);