WP Config: add more URLs to protected web paths

[mshaver]

Description

There are certain WP paths that should be protected from being accessed and are currently resulting in 404 errors. This issue would identify those that we should protect and align with recommendations in https://docs.pantheon.io/pantheon-yml#protected-web-paths

Examples include: /xmlrpc.php

There may be lots of others and a recent site like nsliforyouth.org might be a good place to look for others.

Steps to reproduce

1. Go to https://www.nsliforyouth.org/wp/wp-admin/tools.php?page=redirection.php&sub=404s&groupby=url
2. Notice paths that could be protected

Tech specs