By default, the following tag shows up in every WordPress install.
<link rel="EditURI" type="application/rsd+xml" title="RSD" href="https://yourdomain.com/xmlrpc.php?rsd" />
The above link is used by blog clients. If you edit your site from your browser then you don’t need this. It is also used by some 3rd party applications that utilize XML-RPC requests. In most cases, this is just unnecessary code.
You can easily remove this in the perfmatters plugin by enabling the “Remove RSD Link” option.