[CDEC-285] Remove field accessors for FakeTxsHistory data type

[Jimbo4350]

Description

Remove field accessors for FakeTxsHistory data type

Linked issue

https://iohk.myjetbrains.com/youtrack/issue/CDEC-285

Type of change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• 🛠 New feature (non-breaking change which adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)
• 🏭 Refactoring that does not change existing functionality but does improve things like code readability, structure etc
• 🔨 New or improved tests for existing code
• ⛑ git-flow chore (backport, hotfix, etc)

Developer checklist

• I have read the style guide document, and my code follows the code style of this project.
• If my code deals with exceptions, it follows the guidelines.
• I have updated any documentation accordingly, if needed. Documentation changes can be reflected in opening a PR on cardanodocs.com, amending the inline Haddock comments, any relevant README file or one of the document listed in the docs directory.

Testing checklist

• I have added tests to cover my changes.
• All new and existing tests passed.

QA Steps

Screenshots (if available)

[coot]

Looks good to me, just a small style change to do.

[intricate]

Was the file pkgs/default.nix.new added by mistake?

[Jimbo4350]

After breaking the cardano node in #3140, we are currently writing tests for GenesisConfiguration to be sure we don't do this again. Once we are finished with GenesisConfiguration, we will come back to FakeTxsHistory. Do not merge this branch.

https://iohk.myjetbrains.com/youtrack/issue/CDEC-404

[coot]

@Jimbo4350 note that I added a test for parsing lib/configuration.yaml in #3175

Jordan has fixed it.