build(deps): bump cssbundling-rails from 1.3.0 to 1.3.1

Bumps [cssbundling-rails](https://github.com/rails/cssbundling-rails) from 1.3.0 to 1.3.1.
- [Release notes](https://github.com/rails/cssbundling-rails/releases)
- [Commits](rails/cssbundling-rails@v1.3.0...v1.3.1)

---
updated-dependencies:
- dependency-name: cssbundling-rails
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -124,7 +124,7 @@ GEM
     concurrent-ruby (1.2.2)
     connection_pool (2.4.1)
     crass (1.0.6)
-    cssbundling-rails (1.3.0)
+    cssbundling-rails (1.3.1)
       railties (>= 6.0.0)
     database_cleaner-active_record (2.1.0)
       activerecord (>= 5.a)