Update CHaP index state and flake input

[neilmayhew]

Changelog

- description: |
    Update CHaP index state and flake input
  type:
  - maintenance    # not directly related to the code

Context

This keeps cardano-api in step with cardano-node and cardano-cli

How to trust this PR

See IntersectMBO/cardano-node#6111 and IntersectMBO/cardano-cli#1064

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

[carbolymer]

@neilmayhew could you squash and rebase your commits, please?

[neilmayhew]

The merge queue seems to be having problems. This has failed due to "no response for status checks" three times now. It's strange, though, because all the checks seem to have passed.