How to Remove WordPress Meta Tags http://www.ohdesigner.com/meta-tags-best-practices-for-wordpress/

functions.php

remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
remove_action( 'admin_print_scripts', 'print_emoji_detection_script' );
remove_action( 'wp_print_styles', 'print_emoji_styles' );
remove_action( 'admin_print_styles', 'print_emoji_styles' ); 
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', 10, 0 ); 
remove_action( 'wp_head', 'wp_generator' ); 
remove_action( 'wp_head', 'rest_output_link_wp_head' ); 
remove_action( 'wp_head', 'wp_oembed_add_discovery_links' ); 
remove_action( 'template_redirect', 'rest_output_link_header', 11, 0 );