2 of 4 deleted 755 characters in body; deleted 74 characters in body; added 2 characters in body

I see in filters.php

add_action( 'wp_head', 'rest_output_link_wp_head', 10, 0 );

Which makes me think this should do the trick to remove rel='https://api.w.org/'.

remove_action( 'wp_head',      'rest_output_link_wp_head'              );

The rest... * cough * seem to be in default-filters.php

remove_action( 'wp_head',      'wp_oembed_add_discovery_links'         );