net: disable TestLookupDotsWithRemoteSource and TestLookupGoogleSRV

net: disable TestLookupDotsWithRemoteSource and TestLookupGoogleSRV

These tests fail consistently due to a DNS change causing widespread
trybot outages.

Fixes #56707.

Change-Id: Iebdf91254a922a48880021198f0f12f6bc16b6e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/449640
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>