no_images_links_wordpress.php

//Images without link by default
function wpb_imagelink_setup() {
    $image_set = get_option( 'image_default_link_type' );

    if ($image_set !== 'none') {
        update_option('image_default_link_type', 'none');
    }
}
add_action('admin_init', 'wpb_imagelink_setup', 10);