013dffa65d tests: Use script hash methods (Tobin C. Harding)
Pull request description:
The `ScriptBuf` type can be serialized using it's `to_bytes` function. Do not use the `psbt::Serialize` trait to do so in test code.
No logic changes, since the impl of `psbt::Serialize` for `ScriptBuf` just calls `to_bytes`.
ACKs for top commit:
Kixunil:
ACK 013dffa65d
apoelstra:
ACK 013dffa65d
Tree-SHA512: 08959e065f1528f2ca69c12d5e34bceea3ddd17eefcee45094f071b3fa7357dbf289f6fe54d18fea02eecd1d0a7cd04598bbf014a5f10676387dbe27bb490395