Removing DNS-Prefetch from wp_head hook is a pretty easy task. Just add the following code snippet to your functions to remove DNS-Prefetch links on your header;
// Remove dns-prefetch Link from WordPress Head (Frontend) remove_action( 'wp_head', 'wp_resource_hints', 2 );
What is DNS Prefetch?
DNS prefetching is an attempt to resolve domain names before a user tries to follow a link. This is done using the computer’s normal DNS resolution mechanism; no connection to Google is used.