rpc/ethapi: remove raw field from FillTransactionResult when execution-apis#803 is adopted

[lupin012]

SignTransactionResult.Raw (the raw field in eth_fillTransaction response) is kept for compatibility with current Geth, but ethereum/execution-apis#803 drops it from the spec.

When that PR is merged and adopted, raw must be removed from SignTransactionResult and signedTxJSON.

Tracked here per yperbasis's review of #21870.

[VBulikov]

yperbasis added Imp2 as Importance