chore(registry): replace the docker image for kubectl use (#1416)

Because

- We have to use bitnamisecure/kubectl rather than bitnami/kubectl
docker image

This commit

- replace the docker image for kubectl use

Author: Sarthak-instill

charts/core/templates/registry/maintenance.yaml

@@ -54,7 +54,7 @@ spec:
           serviceAccountName: {{ include "core.registry" . }}-maintenance
           containers:
             - name: kubectl
-              image: bitnami/kubectl
+              image: bitnamisecure/kubectl:latest
               command: ["/bin/bash", "-c"]
               args:
                 - |