You can find the code for this popup in js/functions.js file. Remove the following lines

                    var html = [
                        '<div class="added-to-cart">',
                            '<p>' + basel_settings.added_to_cart + '</p>',
                            '<a href="#" class="btn btn-style-link close-popup">' + basel_settings.continue_shopping + '</a>',
                            '<a href="' + basel_settings.cart_url + '" class="btn btn-color-primary view-cart">' + basel_settings.view_cart + '</a>',
                        '</div>',
                    ].join("");

                    $.magnificPopup.open({
                        items: {
                            src: '<div class="white-popup add-to-cart-popup popup-added_to_cart">' + html + '</div>',
                            type: 'inline'
                        }
                    });

                    $('.white-popup').on('click', '.close-popup', function(e) {
                        e.preventDefault();
                        $.magnificPopup.close();
                    });

But take into account that our theme has minified versions of the script and you need to disable this option in Theme Settings -> Performance to see the result.