Component [app] no longer exists.

[gaaclarke]

The documentation for the appengine package mentions running gcloud components update app but the warning WARNING: Component [app] no longer exists. will appear in the following version:

Google Cloud SDK 280.0.0
bq 2.0.53
core 2020.02.07
gsutil 4.47

[XilaiZhang]

Yeah the app component automatically exists after downloading the gcloud sdk. (https://stackoverflow.com/questions/43244074/cant-access-publicly-exposed-docker-container-port-from-external-machine-only) would be great if author of this repo update the README.md and remove the gcloud components update app line