PLT-6563: Update to cardano-api 8.20

[sjoerdvisscher]

Pre-submit checklist:

• Branch
  • [x] Tests are provided (if possible)
  • [x] Commit sequence broadly makes sense and have useful messages
  • [ ] Important changes are reflected in changelog.d of the affected packages
  • [x] Relevant tickets are mentioned in commit messages
• PR
  • [ ] (For external contributions) Corresponding issue exists and is linked in the description
  • [x] Targeting main unless this is a cherry-pick backport
  • [x] Self-reviewed the diff
  • [x] Useful pull request description
  • [ ] If relevant, reference the ADR in the PR and reference the PR in the ADR
  • [x] Reviewer requested