Change TaprootSpentInfo::output_key type to TweakedPublicKey

[dr-orlovsky]

Code:

rust-bitcoin/src/util/taproot.rs

Line 180 in a84aba1

output_key: schnorr::PublicKey,

We have introduced TweakedPublicKey to clearly distinguish tweaked and untweaked taproot keys, but we missed to use the new type throughout taproot code base :)