Bump pysnmp from 4.4.12 to 7.1.15 in /docker/panw-iot

Bumps [pysnmp](https://github.com/lextudio/pysnmp) from 4.4.12 to 7.1.15.
- [Changelog](https://github.com/lextudio/pysnmp/blob/main/CHANGES.rst)
- [Commits](lextudio/pysnmp@v4.4.12...v7.1.15)

---
updated-dependencies:
- dependency-name: pysnmp
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>