Fix expected reverse lookup of Google DNS IP addresses

DnsTest.testDnsWorks expects that reverse lookup for the Google
public DNS servers will return something with google.com in the
name. This no longer works because the reverse DNS entries have
changed to dns.google.

Bug: 129452237
Test: atest android.net.cts.DnsTest.testDnsWorks
Change-Id: Iee8bfe418bf6003e5c78df77d75f6f9745249267