Make committee hash prefixes CIP-5 compliant

[smelc]

Changelog

- description: |
    bech32 prefixes for committee keys hashes were incorrect. This PR fixes that, in accordance with CIP-5: https://github.com/cardano-foundation/CIPs/blob/master/CIP-0005/README.md?plain=1#L111
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - improvement    # QoL changes e.g. refactoring
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff