revert op-program change

will move to a separate PR

op-program/client/l2/engine.go

@@ -41,23 +41,15 @@ func (o *OracleEngine) L2OutputRoot(l2ClaimBlockNum uint64) (eth.Bytes32, error)
 	if outBlock == nil {
 		return eth.Bytes32{}, fmt.Errorf("failed to get L2 block at %d", l2ClaimBlockNum)
 	}
-	var storageRoot [32]byte
-	// if Isthmus is active, we don't need to compute the storage root, we can use the header
-	// withdrawalRoot which is the storage root for the L2ToL1MessagePasser contract
-	if o.rollupCfg.IsIsthmus(outBlock.Time) {
-		storageRoot = *outBlock.WithdrawalsHash
-	} else {
-		stateDB, err := o.backend.StateAt(outBlock.Root)
-		if err != nil {
-			return eth.Bytes32{}, fmt.Errorf("failed to open L2 state db at block %s: %w", outBlock.Hash(), err)
-		}
-		withdrawalsTrie, err := stateDB.OpenStorageTrie(predeploys.L2ToL1MessagePasserAddr)
-		if err != nil {
-			return eth.Bytes32{}, fmt.Errorf("withdrawals trie unavailable at block %v: %w", outBlock.Hash(), err)
-		}
-		storageRoot = withdrawalsTrie.Hash()
-	}
-	return rollup.ComputeL2OutputRootV0(eth.HeaderBlockInfo(outBlock), storageRoot)
+	stateDB, err := o.backend.StateAt(outBlock.Root)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("failed to open L2 state db at block %s: %w", outBlock.Hash(), err)
+	}
+	withdrawalsTrie, err := stateDB.OpenStorageTrie(predeploys.L2ToL1MessagePasserAddr)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("withdrawals trie unavailable at block %v: %w", outBlock.Hash(), err)
+	}
+	return rollup.ComputeL2OutputRootV0(eth.HeaderBlockInfo(outBlock), withdrawalsTrie.Hash())
 }
 
 func (o *OracleEngine) GetPayload(ctx context.Context, payloadInfo eth.PayloadInfo) (*eth.ExecutionPayloadEnvelope, error) {