Bump pest from 2.5.7 to 2.6.0 in /cmd/zfs_object_agent (openzfs#840)

Bumps [pest](https://github.com/pest-parser/pest) from 2.5.7 to 2.6.0.
- [Release notes](https://github.com/pest-parser/pest/releases)
- [Commits](pest-parser/pest@v2.5.7...v2.6.0)

---
updated-dependencies:
- dependency-name: pest
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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