executor plugins example from documentation does not work

### Pre-requisites

- [X] I have double-checked my configuration
- [X] I have tested with the `:latest` image tag (i.e. `quay.io/argoproj/workflow-controller:latest`) and can confirm the issue still exists on `:latest`. If not, I have explained why, **in detail**, in my description below.
- [X] I have searched existing issues and could not find a match for this bug
- [X] I'd like to contribute the fix myself (see [contributing guide](https://github.com/argoproj/argo-workflows/blob/main/docs/CONTRIBUTING.md))

### What happened/what did you expect to happen?

[Executor_plugins](https://argo-workflows.readthedocs.io/en/stable/executor_plugins/) example provided in the documentation does not work even after adjusting the default service account permissions.

To setup the initial environment I followed the [quick guide](https://argo-workflows.readthedocs.io/en/stable/quick-start/) steps and updated `default` service account RBAC permissions.

```bash
kubectl -n argo apply -f - <

Start with the executor_plugins example and the workflow-rbac and quick-start documentation linked in the issue, then reproduce the workflow manifest against the latest image. Trace the agent pod and controller logs to identify the service account and WorkflowTaskSet permission mismatch. Done means the documented example runs successfully with the documented setup and no incorrect RBAC instructions.

Written by the indexing model from the issue text.