Fixed desired gas limit setting in the reference tests service (#4170)

Signed-off-by: Roman Vaseev <4833306+Filter94@users.noreply.github.com>

Co-authored-by: Justin Florentine <justin+github@florentine.us>

ethereum/retesteth/src/main/java/org/hyperledger/besu/ethereum/retesteth/methods/TestMineBlocks.java

@@ -64,7 +64,7 @@ public class TestMineBlocks implements JsonRpcMethod {
     final PoWBlockCreator blockCreator =
         new PoWBlockCreator(
             context.getCoinbase(),
-            () -> Optional.of(10_000_000L),
+            () -> Optional.of(blockchain.getChainHeadHeader().getGasLimit()),
             header -> context.getExtraData(),
             context.getTransactionPool().getPendingTransactions(),
             protocolContext,