[backport#14678] [wallet] remove redundant KeyOriginInfo access, already done in CreateSig

Summary:
b81a1860561ccbda3cd6913f54e49fdc91c7718c GetPubKey: make sigdata const (Gregory Sanders)
f7beb95a1f921ed292680fbd2f042b4bac73bf59 remove redundant KeyOriginInfo access, already done in CreateSig (Gregory Sanders)

Pull request description:

This redundancy is confusing as it looks like pubkeyhashes are special in some way based on where it's called.

Backport of Core PR14678

Test Plan:

ninja check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6405