Bump sprockets from 3.7.2 to 4.0.0

Bumps [sprockets](https://github.com/rails/sprockets) from 3.7.2 to 4.0.0.
- [Release notes](https://github.com/rails/sprockets/releases)
- [Changelog](https://github.com/rails/sprockets/blob/master/CHANGELOG.md)
- [Commits](rails/sprockets@v3.7.2...v4.0.0)

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

Gemfile.lock

@@ -466,7 +466,7 @@ GEM
     spring-watcher-listen (2.0.1)
       listen (>= 2.7, < 4.0)
       spring (>= 1.2, < 3.0)
-    sprockets (3.7.2)
+    sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-es6 (0.9.2)