go.dev: make cloudbuild.yaml safe to run in golang-org project
go.dev: make cloudbuild.yaml safe to run in golang-org project

Setting --project=go-discovery on the command lines is enough
to do the deploy directly from golang-org Cloud Build, avoiding
an inline cloudbuild.yaml in the trigger configuration that was
reinvoking the cloud build in the other project.

(I gave the golang-org cloud build account permission to be an
"App Engine Deployer" for go-discovery.)

Change-Id: Iafed260f96b9adcf7442a9fa0df2cc44ea28a2ea
Reviewed-on: https://go-review.googlesource.com/c/website/+/328690
Trust: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Run-TryBot: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Jamal Carvalho <e0195770807aa8c82b0b128d9c0423b5ad035172@golang.org>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website