[Doc] update docs that still refer to KFP latest SDK reference

[rui5i]

This PR updates docs that still refer to KFP latest SDK reference.

#4685

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[rui5i]

/assignee @Bobgy

[rui5i]

@googlebot I signed it!

[rui5i]

/assign @Bobgy

[rui5i]

/retest

[rui5i]

/test kubeflow-pipelines-tfx-python36

[Bobgy]

Thanks @rui5i!
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Bobgy, rui5i

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