Thumbnails | Using Jetpack Photon instead

Hello. I plan to disable WooCommerce thumbnail background regeneration using the code:

add_filter( 'woocommerce_background_image_regeneration', '__return_false' );

– Code found on Woocommerce wiki

Can you please tell me, must this code be added to the functions.php file or can I add this code to a functionality plugin and still work correctly?

Thanks for your time and advice!
Julian