Bump shoulda-matchers from 6.2.0 to 6.4.0

Bumps [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers) from 6.2.0 to 6.4.0.
- [Release notes](https://github.com/thoughtbot/shoulda-matchers/releases)
- [Changelog](https://github.com/thoughtbot/shoulda-matchers/blob/main/CHANGELOG.md)
- [Commits](thoughtbot/shoulda-matchers@v6.2.0...v6.4.0)

---
updated-dependencies:
- dependency-name: shoulda-matchers
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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