Update the error message string for tx version too low. ref #1600

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

src/gtest/test_checktransaction.cpp

@@ -100,7 +100,7 @@ TEST(checktransaction_tests, BadVersionTooLow) {
 
     CTransaction tx(mtx);
     MockCValidationState state;
-    EXPECT_CALL(state, DoS(100, false, REJECT_INVALID, "bad-version-too-low", false)).Times(1);
+    EXPECT_CALL(state, DoS(100, false, REJECT_INVALID, "bad-txns-version-too-low", false)).Times(1);
     CheckTransactionWithoutProofVerification(tx, state);
 }
 

src/main.cpp

@@ -854,7 +854,7 @@ bool CheckTransactionWithoutProofVerification(const CTransaction& tx, CValidatio
     // Check transaction version
     if (tx.nVersion < MIN_TX_VERSION) {
         return state.DoS(100, error("CheckTransaction(): version too low"),
-                         REJECT_INVALID, "bad-version-too-low");
+                         REJECT_INVALID, "bad-txns-version-too-low");
     }
 
     // Transactions can contain empty `vin` and `vout` so long as