Enable passing tests (#99)

ethereum/core/src/test/java/tech/pegasys/pantheon/ethereum/vm/BlockchainReferenceTestTools.java

@@ -60,9 +60,6 @@ public class BlockchainReferenceTestTools {
       params.blacklistAll();
     }
 
-    // TODO: Determine and implement cross-chain validation prevention.
-    params.blacklist(
-        "ChainAtoChainB_BlockHash_(Frontier|Homestead|EIP150|EIP158|Byzantium|Constantinople)");
     // Known bad test.
     params.blacklist("RevertPrecompiledTouch_d0g0v0_(EIP158|Byzantium)");