Improve `spo-stake-distribution` help text to clarify its about voting power.

[CarlosLopezDeLara]

Internal/External
Internal if an IOHK staff member.

Area
Governance

Describe the feature you'd like
Improve the help text for spo-stake-distribution cmd to clarify its about voting power. Differentiating from stake-distribution cmd, which i about block producing. They come from different snapshots.

Current descriptions:

  spo-stake-distribution   Get the SPO stake distribution.
  stake-distribution       Get the node's current aggregated stake distribution

[github-actions]

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