build(deps): bump github.com/prometheus/procfs from 0.20.1 to 0.21.0

Bumps [github.com/prometheus/procfs](https://github.com/prometheus/procfs) from 0.20.1 to 0.21.0.
- [Release notes](https://github.com/prometheus/procfs/releases)
- [Commits](https://github.com/prometheus/procfs/compare/v0.20.1...v0.21.0)

---
updated-dependencies:
- dependency-name: github.com/prometheus/procfs
  dependency-version: 0.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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