Bump vimeo/psalm from 5.20.0 to 5.21.0 (#62)

Bumps [vimeo/psalm](https://github.com/vimeo/psalm) from 5.20.0 to 5.21.0.
- [Release notes](https://github.com/vimeo/psalm/releases)
- [Commits](vimeo/psalm@5.20.0...5.21.0)

---
updated-dependencies:
- dependency-name: vimeo/psalm
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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