Bump undercover from 0.8.3 to 0.8.4

Bumps [undercover](https://github.com/grodowski/undercover) from 0.8.3 to 0.8.4.
- [Release notes](https://github.com/grodowski/undercover/releases)
- [Changelog](https://github.com/grodowski/undercover/blob/master/CHANGELOG.md)
- [Commits](https://github.com/grodowski/undercover/compare/v0.8.3...v0.8.4)

---
updated-dependencies:
- dependency-name: undercover
  dependency-version: 0.8.4
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -916,7 +916,7 @@ GEM
       turbo-rails (>= 1.3.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    undercover (0.8.3)
+    undercover (0.8.4)
       base64
       bigdecimal
       imagen (>= 0.2.0)