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] <support@github.com>

Gemfile.lock

@@ -372,7 +372,7 @@ GEM
     method_source (1.1.0)
     mini_mime (1.1.5)
     mini_portile2 (2.8.8)
-    minitest (5.25.1)
+    minitest (5.25.2)
     mixlib-cli (2.1.8)
     mixlib-config (3.0.27)
       tomlrb
@@ -569,7 +569,7 @@ GEM
       rack-proxy (>= 0.6.1)
       railties (>= 5.2)
       semantic_range (>= 2.3.0)
-    shoulda-matchers (6.2.0)
+    shoulda-matchers (6.4.0)
       activesupport (>= 5.2.0)
     sidekiq (6.5.5)
       connection_pool (>= 2.2.2)