unregister_block_type example

function register_legacy_post_comments_block() {
    $registry = WP_Block_Type_Registry::get_instance();

    /* * Remove the old `post-comments` block if it was already registered, as it * is about to be replaced by the type defined below. */
    if ( $registry->is_registered( 'core/post-comments' ) ) {
        unregister_block_type( 'core/post-comments' );
    }

    // Recreate the legacy block metadata.     $metadata = array(
        'name'              => 'core/post-comments',
        'category'          => 'theme',
        'attributes'        => array(
            'textAlign' => array(
                'type' => 'string',
            ),
        ),