Rename FluentCart Categories.php

<?php
add_filter( 'taxonomy_labels_product-categories', function( $labels ) {
    $labels->name          = 'FluentCartProduct Categories';
    $labels->singular_name = 'FluentCartProduct Category';
    $labels->menu_name     = 'FluentCartProduct Categories';
    $labels->all_items     = 'All FluentCartProduct Categories';
    $labels->edit_item     = 'Edit FluentCartProduct Category';
    $labels->add_new_item  = 'Add New FluentCartProduct Category';

    return $labels;
});