Unregister custom post type from Wordpress

I was able to remove it in WordPress 4.6.1 using this code:

function delete_post_type(){
  unregister_post_type( 'portfolio' );
}
add_action('init','delete_post_type', 100);

Your code look good! But if you unregister the post_type... the posts in it go away... So don't unregister it too soon. Before you unregister the post type, migrate the posts from the post_type to normal posts. This plugin is handy for that: https://wordpress.org/plugins/post-type-switcher/

But if you don't want to migrate the video posts to the default posts... You'll have to modify your loop to include those portfolio-type posts:

function add_custom_post_type_to_query( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'post_type', array('post', 'portfolio') );
    }
}
add_action( 'pre_get_posts', 'add_custom_post_type_to_query' );

& don't forget to visit the permalinks page when working with custom post types to get WordPress to recognize the changes you've made.