Drop redundant PParamsUpdate round-trip in update proposal flow
`makeShelleyUpdateProposal` (cardano-api ^>=11.1) accepts `EraBasedProtocolParametersUpdate era` directly. The existing code in `shelleyToBabbageProtocolParametersUpdate` constructed that value, converted it to the deprecated `ProtocolParametersUpdate` via `createEraBasedProtocolParamUpdate` / `fromLedgerPParamsUpdate`, and passed the result to `makeShelleyUpdateProposal` — an unnecessary round-trip through the old API. Drop the conversion; pass `eraBasedPParams` directly. No behaviour change.