chore: remove timestamp hack (#2471)

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## Overview

This pr removes the +1 timestamp in order to avoid clock drift between
lumen and rollkit.

closes #2464 

based off of work from evstack/ev-reth#19

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Refactor**
* Simplified block timestamp handling to use the current block's
timestamp directly, removing previous logic that enforced strictly
increasing timestamps between blocks.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: tac0turtle <you@example.com>

Author: tac0turtle

execution/evm/execution.go

@@ -181,16 +181,11 @@ func (c *EngineClient) ExecuteTxs(ctx context.Context, txs [][]byte, blockHeight
 		txsPayload[i] = "0x" + hex.EncodeToString(tx)
 	}
 
-	prevBlockHash, _, prevGasLimit, prevTimestamp, err := c.getBlockInfo(ctx, blockHeight-1)
+	prevBlockHash, _, prevGasLimit, _, err := c.getBlockInfo(ctx, blockHeight-1)
 	if err != nil {
 		return nil, 0, fmt.Errorf("failed to get block info: %w", err)
 	}
 
-	ts := uint64(timestamp.Unix())
-	if ts <= prevTimestamp {
-		ts = prevTimestamp + 1 // Subsequent blocks must have a higher timestamp.
-	}
-
 	args := engine.ForkchoiceStateV1{
 		HeadBlockHash:      prevBlockHash,
 		SafeBlockHash:      prevBlockHash,
@@ -203,7 +198,7 @@ func (c *EngineClient) ExecuteTxs(ctx context.Context, txs [][]byte, blockHeight
 	// Create rollkit-compatible payload attributes with flattened structure
 	rollkitPayloadAttrs := map[string]interface{}{
 		// Standard Ethereum payload attributes (flattened) - using camelCase as expected by JSON
-		"timestamp":             ts,
+		"timestamp":             timestamp.Unix(),
 		"prevRandao":            c.derivePrevRandao(blockHeight),
 		"suggestedFeeRecipient": c.feeRecipient,
 		"withdrawals":           []*types.Withdrawal{},