:bug: fix topics in koan AboutComparison

[peetrike]

PR Summary

fixes #450

Context

Changes

• fix topic 'It will compare values'
• fix topic 'It returns $true only if both inputs are $true'
• fix topic 'It may coerce values to boolean' (in context '-or')

Checklist

• [x] Pull Request has a meaningful title.
• [x] Summarised changes.
• [x] Pull Request is ready to merge & is not WIP.
• [x] Added tests / only testable interactively.
  • Make sure you add a new test if old tests do not effectively test the code changed.
• [x] Added documentation / opened issue to track adding documentation at a later date.