Whitelist DoH servers in the network auditor (brave/brave-browser#1864)

This is needed because the Mac build machines use these OS
resolvers:

    nameserver 8.8.8.8
    nameserver 8.8.4.4
    nameserver 1.1.1.1
    nameserver 1.0.0.1

build/commands/lib/whitelistedUrlPrefixes.js

@@ -28,5 +28,7 @@ module.exports = [
   'https://pdfjs.robwu.nl/logpdfjs', // allowed because it gets canceled in tracking protection
   'https://publishers-distro.basicattentiontoken.org/',
   'https://publishers-staging-distro.basicattentiontoken.org/',
-  'https://p3a.brave.com/'
+  'https://p3a.brave.com/',
+  'https://dns.google/dns-query', // needed for DoH on Mac build machines
+  'https://chrome.cloudflare-dns.com/dns-query', // needed for DoH on Mac build machines
 ]