[App][CLI] Fix lightning cli --version

[manskx]

What does this PR do?

Fixes #14410

Also deleting some dead code.

Does your PR introduce any breaking changes? If yes, please list them.

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cc @Borda

[awaelchli]

We could add a changelog entry as well

[manskx]

We could add a changelog entry as well

added

[tchaton]

LGTM !