Remove outdated examples from the `PowerDistributingActor`

[mathias-baumann-frequenz]

What happened?

The example provided in the comments for the PowerDistributingActor is rather outdated and needs updating.

Additionally some general explanation how it works in the first place and what a user can do with it would be helpful.

What did you expect instead?

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Affected version(s)

No response

Affected part(s)

Documentation (part:docs)

Extra information

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