[WAL-1454] FCA-compliance text changes

[Ivan-Mahda]

Purpose

We have to make these changes across the wallet for us to be FCA legally compliant and pass the KYB (know your business)

Changes

Change Earn -> Stake

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.
• (If necessary) I have updated the CHANGELOG.