Small correction to workflow template dag example

[dynamicmindset]

Summary

What change needs making?

dag example passes arguments to a DagTemplate ref that does not have inputs.

      - name: C
        dependencies: [A]
        templateRef:
          name: workflow-template-inner-dag
          template: inner-diamond
        arguments:
          parameters:
          - name: message
            value: C

This can be confusing for a newcomer.

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Message from the maintainers:

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[alexec]

Available for testing in v2.11.0-rc1.