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.

.ci-mgmt.yaml

@@ -9,21 +9,12 @@ gcp: true
 sdkModuleDir: sdk/go/dockerbuild
 parallel: 3
 esc:
-    enabled: true
+  enabled: true
 envOverride:
-    AWS_REGION: us-west-2
-    PULUMI_API: "https://api.pulumi-staging.io"
-    ARM_CLIENT_ID: 30e520fa-12b4-4e21-b473-9426c5ac2e1e
-    ARM_SUBSCRIPTION_ID: 0282681f-7a9e-424b-80b2-96babd57a8a1
-    ARM_TENANT_ID: 706143bc-e1d4-4593-aee2-c9dc60ab9be7
-    ARM_CLIENT_SECRET: ${{ secrets.ARM_CLIENT_SECRET }}
-    AZURE_LOCATION: westus
-    DIGITALOCEAN_TOKEN: ${{ secrets.DIGITALOCEAN_TOKEN }}
-    GOOGLE_CI_SERVICE_ACCOUNT_EMAIL: pulumi-ci@pulumi-ci-gcp-provider.iam.gserviceaccount.com
-    GOOGLE_CI_WORKLOAD_IDENTITY_POOL: pulumi-ci
-    GOOGLE_CI_WORKLOAD_IDENTITY_PROVIDER: pulumi-ci
-    GOOGLE_PROJECT: pulumi-ci-gcp-provider
-    GOOGLE_PROJECT_NUMBER: 895284651812
-    GOOGLE_REGION: us-central1
-    GOOGLE_ZONE: us-central1-a
-    DOCKER_HUB_PASSWORD: ${{ secrets.DOCKER_HUB_PASSWORD }}
+  GOOGLE_CI_SERVICE_ACCOUNT_EMAIL: pulumi-ci@pulumi-ci-gcp-provider.iam.gserviceaccount.com
+  GOOGLE_CI_WORKLOAD_IDENTITY_POOL: pulumi-ci
+  GOOGLE_CI_WORKLOAD_IDENTITY_PROVIDER: pulumi-ci
+  GOOGLE_PROJECT: pulumi-ci-gcp-provider
+  GOOGLE_PROJECT_NUMBER: "895284651812"
+  GOOGLE_REGION: us-central1
+  GOOGLE_ZONE: us-central1-a