Remove usage of deprecated ContainerOp methods in use_gcp_secret

[andrewsmartin]

This change is 

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[k8s-ci-robot]

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[Ark-kun]

Thank you fro cleaning it up!
/lgtm

[Ark-kun]

/retest

[Ark-kun]

/approve

BTW, in what environment do you see the deprecation warnings? I do not see them when working in a notebook.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Ark-kun

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