Incorrect error checking in SyncingWithInvalidChain test

[Tumas]

It looks like this error checking condition is incorrect and needs to be inverted:

hive/simulators/eth2/engine/scenarios.go

Lines 1243 to 1247 in d7cb48a

	if payload, err := versionedBlock.ExecutionPayload(); err == nil {
	t.Fatalf(
	"FAIL: error getting execution payload: %v",
	err,
	)

as ExecutionPayload method returns no error when payload is returned.