Bump shoulda-matchers from 6.3.1 to 6.4.0

Bumps [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers) from 6.3.1 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@v6.3.1...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]>

Gemfile.lock

@@ -110,7 +110,7 @@ GEM
       net-smtp
     marcel (1.0.4)
     mini_mime (1.1.5)
-    minitest (5.25.0)
+    minitest (5.25.1)
     msgpack (1.7.2)
     net-imap (0.4.14)
       date
@@ -224,7 +224,7 @@ GEM
       rubocop-ast (>= 1.31.1, < 2.0)
     ruby-progressbar (1.13.0)
     securerandom (0.3.1)
-    shoulda-matchers (6.3.1)
+    shoulda-matchers (6.4.0)
       activesupport (>= 5.2.0)
     stringio (3.1.1)
     strscan (3.1.0)