Thanks to TheDeadMedic I found the solution in "wp-includes/default-filters.php". The following removes the next and prev links from wp_head:
remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0 );
This is the full script for removing all "unnecessary" meta tags from the <head>
:
//remove_action( 'wp_head', 'wp_enqueue_scripts', 1 );
remove_action( 'wp_head', 'feed_links', 2 );
remove_action( 'wp_head', 'feed_links_extra', 3 );
remove_action( 'wp_head', 'rsd_link' );
remove_action( 'wp_head', 'wlwmanifest_link' );
remove_action( 'wp_head', 'index_rel_link' );
remove_action( 'wp_head', 'parent_post_rel_link', 10, 0 );
remove_action( 'wp_head', 'start_post_rel_link', 10, 0 );
remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0 );
remove_action( 'wp_head', 'locale_stylesheet' );
remove_action( 'publish_future_post', 'check_and_publish_future_post', 10, 1 );
//remove_action( 'wp_head', 'noindex', 1 );
remove_action( 'wp_head', 'wp_print_styles', 8 );
remove_action( 'wp_head', 'wp_print_head_scripts', 9 );
remove_action( 'wp_head', 'wp_generator' );
//remove_action( 'wp_head', 'rel_canonical' );
remove_action( 'wp_footer', 'wp_print_footer_scripts' );
remove_action( 'wp_head', 'wp_shortlink_wp_head', 10, 0 );
remove_action( 'template_redirect', 'wp_shortlink_header', 11, 0 );
add_action('widgets_init', 'my_remove_recent_comments_style');
function my_remove_recent_comments_style() {
global $wp_widget_factory;
remove_action('wp_head', array($wp_widget_factory->widgets['WP_Widget_Recent_Comments'], 'recent_comments_style'));
}