Two Docker warnings when using sample hello-app project

[nunokaeru]

When following the quickstarts/hello-app example the following Docker warnings are emitted:

 2 warnings found (use docker --debug to expand):
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 16)
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 25)

This happens during the step:

Build the image

GKE accepts Docker images as the application deployment format. Before deploying the hello-app application, you must package the source code as a Docker image.

To build a Docker image, you need source code and a Dockerfile. A Dockerfile contains instructions on how the image is built.

    Build and tag the Docker image for hello-app:

docker build -t ${REGION}-docker.pkg.dev/${PROJECT_ID}/hello-repo/hello-app:v1 .

This command instructs Docker to build the image using the Dockerfile in the current directory and tag it with a name, such as us-west1-docker.pkg.dev/my-project/hello-repo/hello-app:v1. The image is pushed to Artifact Registry in the next section

Should these be fixed for all other sample projects as well?