txscript: fix sighash bug in RawTxInTaprootSignature

In this commit, we fix a bug in RawTxInTaprootSignature that would cause
the function to not properly apply the sighash flag for non-default
sighash signatures. The logic would end up applying `0x00` as a mask,
which will always be `0x00` on the other end.

The RawTxInTapscriptSignature function was correct, though it had the
ordering switched as it applies the sighash if the type doesn't equal
default.

txscript/sign.go

@@ -95,7 +95,7 @@ func RawTxInTaprootSignature(tx *wire.MsgTx, sigHashes *TxSigHashes, idx int,
 
 	// If this is sighash default, then we can just return the signature
 	// directly.
-	if hashType&SigHashDefault == SigHashDefault {
+	if hashType == SigHashDefault {
 		return sig, nil
 	}