fix misc places that refer to virtual transaction size

Summary:
At the moment there's no used concept of virtual size. Perhaps it will come
in later (and this can be reverted) but for now this is more accurate.

Test Plan: ninja check-all

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D4910