Bump sprockets from 4.1.1 to 4.2.1

Bumps [sprockets](https://github.com/rails/sprockets) from 4.1.1 to 4.2.1.
- [Release notes](https://github.com/rails/sprockets/releases)
- [Changelog](https://github.com/rails/sprockets/blob/main/CHANGELOG.md)
- [Commits](rails/sprockets@v4.1.1...v4.2.1)

---
updated-dependencies:
- dependency-name: sprockets
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -422,9 +422,9 @@ GEM
     snaky_hash (2.0.1)
       hashie
       version_gem (~> 1.1, >= 1.1.1)
-    sprockets (4.1.1)
+    sprockets (4.2.1)
       concurrent-ruby (~> 1.0)
-      rack (> 1, < 3)
+      rack (>= 2.2.4, < 4)
     sprockets-rails (3.4.2)
       actionpack (>= 5.2)
       activesupport (>= 5.2)