5b21a9cb1f Use TapTweakHash method for computing tweak (Noah)
Pull request description:
Quick follow up PR to #691 using a method from #677.
### Changes
- Updated `UntweakedPublicKey::tap_tweak(...)` to use `TapTweakHash::from_key_and_tweak(...)`
ACKs for top commit:
Kixunil:
ACK 5b21a9cb1f
dr-orlovsky:
utACK 5b21a9cb1f
Tree-SHA512: d00455bba51981e9ec942a6cf69672666e227850d073b1fdcd92d2eb6ad553659fb2967aec2ce12d3ed109cee5fa125cdda649cddb25404f08adae2bfd3e19bb