gnu: python-trezor-agent: Update to 0.13.0.

* gnu/packages/finance.scm (python-trezor-agent): Update to 0.13.0.
[propagated-inputs]: Add python-configargparse, python-daemon,
python-docutils, python-mnemonic, python-pymsgbox, python-wheel.
[native-inputs]: Add gnupg.
[synopsis]: Generalize description to hardware wallets.
[arguments]<#:phases>[remove-requires-backports-shutil-which]: New phase.