Deleted mentioning of Nano S in various files throughout documentation

[TinaKT]

Purpose

To remove mentioning of the Nano S ledger device from documentation.

Changes

Removed mentioning of the Nano S in various files throughout documentation. Either removed it completely or replaced it with "ledger device", depending on the context.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.

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Contributor License Agreement v1.0

• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf