Cacher is the code snippet organizer for pro developers

add_filter( 'product_type_selector' , 'woo_custom_product_type_selector' );

/**
 * Removes all product types from product type dropdown select
 * except "simple product"
 *
 * @access      public
 * @since       1.0 
 * @return      void
*/

function woo_custom_product_type_selector() {
	
	$product_type_selector = array(
								'simple' 	=> __( 'Simple product', 'woocommerce' ),
							);
							
	return $product_type_selector;
	
}