Add text above cart form @ WooCommerce single product if in particular category

single-product-category-notice.php

add_action( 'woocommerce_before_add_to_cart_form', 'category_notice' );

function category_notice() {
    if (has_term('accessories', 'product_cat')) { // Replace 'accessories' with your category
        echo '<div class="category_notice"><p>This is a notice.</p></div>';
    }
}