[Standalone] Fix GCP cloudsql manifest

[Bobgy]

Fixes #2719

Decisions

• I wanted to patch only related entries in the JSON configmap, but this isn't currently supported by kustomize: Patch literal JSON in ConfigMap item kubernetes-sigs/kustomize#680, we can only duplicate it.

Verification

$ kubectl kustomize env/gcp/ | grep workflow-controller-configmap -C 30
    component: metadata-server
  name: metadata-mysql-configmap
  namespace: kubeflow
---
apiVersion: v1
data:
  config: |
    {
    namespace: kubeflow,
    executorImage: gcr.io/ml-pipeline/argoexec:v2.3.0-license-compliance,
    artifactRepository:
    {
        s3: {
            bucket: '', # Replace this with the same bucket as OBJECTSTORECONFIG_BUCKETNAME.
            keyPrefix: artifacts,
            endpoint: minio-service.kubeflow:9000,
            insecure: true,
            accessKeySecret: {
                name: mlpipeline-minio-artifact,
                key: accesskey
            },
            secretKeySecret: {
                name: mlpipeline-minio-artifact,
                key: secretkey
            }
        }
    }
    }
kind: ConfigMap
metadata:
  name: workflow-controller-configmap
  namespace: kubeflow
---

namespace replacement works well too

---

This change is 

[jingzhang36]

/lgtm

[Bobgy]

/approve

[k8s-ci-robot]

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