Fix NegateSignatureS to not duplicate last byte of S

NegateSignatureS is called with a signature without a hashtype, so
do not save the last byte and append it after S negation.

Updates the two tests which were affected by this bug.

src/test/data/script_invalid.json

@@ -696,7 +696,7 @@
     "BIP66 example 11, with DERSIG"
 ],
 [
-    "0x49 0x304502203e4516da7253cf068effec6b95c41221c0cf3a8e6ccb8cbf1725b562e9afde2c022100ab1e3da73d67e32045a20e0b999e049978ea8d6ee5480d485fcf2ce0d03b2ef05101",
+    "0x48 0x304502203e4516da7253cf068effec6b95c41221c0cf3a8e6ccb8cbf1725b562e9afde2c022100ab1e3da73d67e32045a20e0b999e049978ea8d6ee5480d485fcf2ce0d03b2ef001",
     "0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 CHECKSIG",
     "LOW_S",
     "P2PK with high S"

src/test/data/script_valid.json

@@ -814,7 +814,7 @@
     "BIP66 example 12, with DERSIG"
 ],
 [
-    "0x49 0x304502203e4516da7253cf068effec6b95c41221c0cf3a8e6ccb8cbf1725b562e9afde2c022100ab1e3da73d67e32045a20e0b999e049978ea8d6ee5480d485fcf2ce0d03b2ef05101",
+    "0x48 0x304502203e4516da7253cf068effec6b95c41221c0cf3a8e6ccb8cbf1725b562e9afde2c022100ab1e3da73d67e32045a20e0b999e049978ea8d6ee5480d485fcf2ce0d03b2ef001",
     "0x21 0x03363d90d447b00c9c99ceac05b6262ee053441c7e55552ffe526bad8f83ff4640 CHECKSIG",
     "",
     "P2PK with high S but no LOW_S"

src/test/script_tests.cpp

@@ -107,7 +107,6 @@ void static NegateSignatureS(std::vector<unsigned char>& vchSig) {
     std::vector<unsigned char> r, s;
     r = std::vector<unsigned char>(vchSig.begin() + 4, vchSig.begin() + 4 + vchSig[3]);
     s = std::vector<unsigned char>(vchSig.begin() + 6 + vchSig[3], vchSig.begin() + 6 + vchSig[3] + vchSig[5 + vchSig[3]]);
-    unsigned char hashtype = vchSig.back();
 
     // Really ugly to implement mod-n negation here, but it would be feature creep to expose such functionality from libsecp256k1.
     static const unsigned char order[33] = {
@@ -141,7 +140,6 @@ void static NegateSignatureS(std::vector<unsigned char>& vchSig) {
     vchSig.push_back(0x02);
     vchSig.push_back(s.size());
     vchSig.insert(vchSig.end(), s.begin(), s.end());
-    vchSig.push_back(hashtype);
 }
 
 namespace