guix: update time-machine
Summary:
python-altgraph (0.17.4) has been upstreamed, see: https://git.savannah.gnu.org/cgit/guix.git/commit/?id=0c6198319a61d85cd8925af418466dcdccf3daff, so we can use it, and drop our package definition.
Backport of core#28580.
Depends on D17229.
Test Plan: Run the GUIX OSX build.
Reviewers: #bitcoin_abc, PiRK
Reviewed By: #bitcoin_abc, PiRK
Differential Revision: https://reviews.bitcoinabc.org/D17230