itest: fix make lint

This commit fixes the issues reported by the linter.

itest/lnd_forward_interceptor_test.go

@@ -416,6 +416,7 @@ func (c *interceptorTestScenario) prepareTestCases() []*interceptorTestCase {
 		t.invoice = invoice
 		t.payAddr = payReq.PaymentAddr
 	}
+
 	return cases
 }