deps: bump pyhanko from 0.20.1 to 0.25.0

Bumps [pyhanko](https://github.com/MatthiasValvekens/pyHanko) from 0.20.1 to 0.25.0.
- [Release notes](https://github.com/MatthiasValvekens/pyHanko/releases)
- [Changelog](https://github.com/MatthiasValvekens/pyHanko/blob/master/docs/changelog.rst)
- [Commits](MatthiasValvekens/pyHanko@v0.20.1...v0.25.0)

---
updated-dependencies:
- dependency-name: pyhanko
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -4,4 +4,4 @@ scapy
 parsimonious
 asn1crypto
 dpkt
-pyhanko==0.20.1
+pyhanko==0.25.0