D0 instances outdated

[elharo]

I got lost at the point "Sign up for a Google Cloud Platform project, and set up a Cloud SQL instance, as described here. To keep costs down, we suggest signing up for a D0 instance with package billing."

On further investigation, it appears that this is a term applicable to first generation instances only, but the linked instructions ("described here") strongly recommended using a second generation instance.

Please update the tutorial to either recommend the first generation instance, or specify an instance size that makes sense for a second generation instance.