Remove unnecessary envOverride (#766)

Our DockerHub password is in ESC, and a bunch of the other variables
were copy-pasted defaults. We need to keep GCP because that isn't in
ESC yet.

Refs https://github.com/pulumi/ci-mgmt/issues/1583.

examples/tests/ecr/Pulumi.yaml

@@ -38,3 +38,5 @@ variables:
   auth-token:
     fn::aws:ecr:getAuthorizationToken:
       registryId: ${ecr-repository.registryId}
+config:
+  aws:region: us-west-2