Specify IsRecentEra constraint in buildCoinSelectionForTransaction.

We only support building transactions in "recent eras", and
"IsRecentEra" already provides us with the superclass constraint that
was missing, so using it kills two birds with one stone.

lib/wallet/src/Cardano/Wallet.hs

@@ -1696,7 +1696,7 @@ data CoinSelection = CoinSelection
 
 buildCoinSelectionForTransaction
     :: forall s k n era
-     . ( Cardano.IsCardanoEra era
+     . ( WriteTx.IsRecentEra era
        , IsOurs s Address
        , s ~ SeqState n k
        )