google: ignore declare_namespace deprecation warnings (#9604)

Fixes the nopin build on master.

---------

Co-authored-by: Brad Warren <bmw@users.noreply.github.com>

pytest.ini

@@ -21,9 +21,12 @@
 #    updated.
 # 4) Ignore our own PendingDeprecationWarning about update_symlinks soon to be dropped.
 #    See https://github.com/certbot/certbot/issues/6284.
+# 5) Ignore pkg_resources.declare_namespace used in a large number of Google's Python
+#    libs. e.g. https://github.com/googleapis/google-auth-library-python/issues/1229.
 filterwarnings =
     error
     ignore:decodestring\(\) is a deprecated alias:DeprecationWarning:dns
     ignore:.*rsyncdir:DeprecationWarning
     ignore:'urllib3.contrib.pyopenssl:DeprecationWarning:requests_toolbelt
     ignore:update_symlinks is deprecated:PendingDeprecationWarning
+    ignore:.*declare_namespace\('google:DeprecationWarning