Make doctests work with ghc-9.14

```shellsession
$ nix develop .#ghc9141
$ cabal build all && scripts/doctest.sh
...
.../libs/cardano-ledger-api/src/Cardano/Ledger/Api/Tx.hs:18: failure in expression `import Cardano.Ledger.Api.Era (BabbageEra)'
expected:
but got: : error: [GHC-87110]
^
Could not load module ‘Cardano.Ledger.Api.Era’.
It is a member of the hidden package ‘cardano-ledger-api-1.13.0.0’.
Perhaps you need to add ‘cardano-ledger-api’ to the build-depends in your .cabal file.

.../libs/cardano-ledger-api/src/Cardano/Ledger/Api/Tx/Out.hs:17: failure in expression `import Cardano.Ledger.Api.Era (BabbageEra)'
expected:
but got: : error: [GHC-87110]
^
Could not load module ‘Cardano.Ledger.Api.Era’.
It is a member of the hidden package ‘cardano-ledger-api-1.13.0.0’.
Perhaps you need to add ‘cardano-ledger-api’ to the build-depends in your .cabal file.

.../libs/cardano-ledger-api/src/Cardano/Ledger/Api/Era.hs:167: failure in expression `import Cardano.Ledger.Api.Era (BabbageEra, ConwayEra)'
expected:
but got: : error: [GHC-87110]
^
Could not load module ‘Cardano.Ledger.Api.Era’.
It is a member of the hidden package ‘cardano-ledger-api-1.13.0.0’.
Perhaps you need to add ‘cardano-ledger-api’ to the build-depends in your .cabal file.

Examples: 25 Tried: 8 Errors: 0 Failures: 3
```

_Originally requested by @lehins in https://github.com/IntersectMBO/cardano-ledger/issues/5599#issuecomment-4041243118_