guix: use osslsigncode 2.5

Summary:
Co-authored-by: Andrew Chow <github@achow101.com>

This is a backport of core#27179

Depends on D15325

Test Plan: contrib/guix/guix-build

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15326