PipelineTaskFinalStatus is only available for VertexAI pipelines

[j-faustin-instadeep]

The documentation concerning Control Flow and the ExitHandler should mention that the PipelineTaskFinalStatus class featured in the example is only available for VertexAI pipelines.

I tried experimenting with this example using a local deployment of KubeFlow pipelines. Compilation seemed to go fine but running the pipeline failed with an error: "(...) failed to add implicit deps: task final status not supported yet (...)".

I suggest:

1. Explicitly mention that PipelineTaskFinalStatus is not supported for the KFP backend as it is done above for dsl.Collected
2. Add a new example of exit_op compatible with the KFP backend.

https://www.kubeflow.org/docs/components/pipelines/v2/pipelines/control-flow/#exit-handling-dslexithandler