Piece of code that I use regularly to unregister a WordPress post type. Just add/edit/remove the post type from lines 3, 4 and 5 and paste in your functions.php file.

snippet.php

<?php
// Download this snippet as a plugin and more at: https://wordbits.io/snippet/unregister-wordpress-post-types/
// Created by: Metal Potato
?>

<?php
function well_delete_post_type(){
    unregister_post_type( 'portfolio' );
    unregister_post_type( 'cms_block' );
    unregister_post_type( 'uncode_gallery' );    
    
}
add_action('init','well_delete_post_type');