Bump pin from 2.6.17 to 2.6.20

Bumps [pin](https://github.com/stack-of-tasks/pinocchio) from 2.6.17 to 2.6.20.
- [Release notes](https://github.com/stack-of-tasks/pinocchio/releases)
- [Commits](stack-of-tasks/pinocchio@v2.6.17...v2.6.20)

---
updated-dependencies:
- dependency-name: pin
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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