Generate non-preferred APIs by default

Warn instead of failing on Discovery URL requests that error. Some
URLs on the Discovery index return 404s, so skipping them saves trouble.

script/generate

@@ -8,9 +8,7 @@ URLS=(https://content.googleapis.com/discovery/v1/apis/appsmarket/v2/rest \
       https://content.googleapis.com/discovery/v1/apis/youtubePartner/v1/rest \
       https://content.googleapis.com/discovery/v1/apis/compute/beta/rest \
       https://developers.google.com/my-business/samples/mybusiness_google_rest_v3.json \
-      https://monitoring.googleapis.com/\$discovery/rest?version=v3 \
-      https://www.googleapis.com/discovery/v1/apis/admin/datatransfer_v1/rest \
-      https://www.googleapis.com/discovery/v1/apis/admin/directory_v1/rest
+      https://monitoring.googleapis.com/\$discovery/rest?version=v3
 )
 
-echo 'a' | bundle exec bin/generate-api gen generated --from_discovery=true --names_out=$DIR/api_names_out.yaml --url=${URLS[*]}
+echo 'a' | bundle exec bin/generate-api gen generated --from-discovery --no-preferred-only --names-out=$DIR/api_names_out.yaml --url=${URLS[*]}