function my_deregister_scripts(){
 wp_dequeue_script( 'wp-embed' );
}
add_action( 'wp_footer', 'my_deregister_scripts' );

ref.
+https://codex.wordpress.org/Embeds
+https://wordpress.stackexchange.com/questions/211701/what-does-wp-embed-min-js-do-in-wordpress-4-4
+https://wordpress.stackexchange.com/questions/202496/disable-automatic-oembed-of-a-youtube-url-within-the-content
+https://wordpress.stackexchange.com/questions/267127/how-to-disable-youtube-and-any-other-oembed-embeding-in-the-editor