How to remove quantity button on the bottom of the product page

Site URL: https://www.primarypurify.com/

I would like to know how to remove the quantity button from the product page.

I attached an image below. The button I am referring to is in between the "select amount" button and the "add to cart button"

Add to Home > Design > Custom CSS

.product-quantity-input {
    display: none !important;
}