Bump sprockets from 3.7.2 to 4.2.1

Bumps [sprockets](https://github.com/rails/sprockets) from 3.7.2 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@v3.7.2...v4.2.1)

---
updated-dependencies:
- dependency-name: sprockets
  dependency-type: indirect
  update-type: version-update:semver-major
...

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

Gemfile.lock

@@ -161,7 +161,7 @@ GEM
       ttfunk
     public_suffix (5.0.4)
     racc (1.7.3)
-    rack (2.2.7)
+    rack (2.2.8)
     rack-livereload (0.3.17)
       rack
     rainbow (3.1.1)
@@ -181,9 +181,9 @@ GEM
     sassc (2.4.0)
       ffi (~> 1.9)
     servolux (0.13.0)
-    sprockets (3.7.2)
+    sprockets (4.2.1)
       concurrent-ruby (~> 1.0)
-      rack (> 1, < 3)
+      rack (>= 2.2.4, < 4)
     temple (0.10.3)
     thor (1.2.2)
     tilt (2.0.11)