You have forgotten the filter hook:
add_filter( 'woocommerce_product_tabs', 'woo_customize_tabs', 100, 1 );
function woo_customize_tabs( $tabs ) {
unset($tabs['reviews']); // Remove the reviews tab
$tabs['description']['title'] = __( 'More Information' ); // Rename the description tab
return $tabs;
}
Code goes in function.php file of your active child theme (or theme) or also in any plugin file.
All code is tested on Woocommerce 3+ and works.
Update (related to your comment) | Rename product description heading (inside the tab):
To rename description heading use woocommerce_product_description_heading filter hook this way:
add_filter( 'woocommerce_product_description_heading', 'rename_product_description_heading', 10, 1 );
function rename_product_description_heading( $heading ) {
return __( 'Additional Information', 'woocommerce' );
}
Code goes in function.php file of your active child theme (or theme) or also in any plugin file.
All code is tested on Woocommerce 3+ and works.
Official related documentation: Editing product data tabs