Reuse type level tags for Babbage and ConwayEra

cardano-api/internal/Cardano/Api/Experimental/Eras.hs

@@ -37,6 +37,7 @@ import           Cardano.Api.Eon.BabbageEraOnwards
 import           Cardano.Api.Eon.ShelleyBasedEra (ShelleyBasedEra (..), ShelleyLedgerEra)
 import qualified Cardano.Api.Eras.Core as Api
 import           Cardano.Api.Via.ShowOf
+import Cardano.Api.Eras.Core(BabbageEra, ConwayEra)
 import qualified Cardano.Api.ReexposeLedger as L
 import qualified Cardano.Ledger.Api as L
 import qualified Cardano.Ledger.UTxO as L
@@ -54,9 +55,6 @@ import           Prettyprinter
 -- | Users typically interact with the latest features on the mainnet or experiment with features
 -- from the upcoming era. Hence, the protocol versions are limited to the current mainnet era
 -- and the next era (upcoming era).
-data BabbageEra
-
-data ConwayEra
 
 -- Allows us to gradually change the api without breaking things.
 -- This will eventually be removed.