Bump autoprefixer-rails from 10.4.13.0 to 10.4.15.0

Bumps [autoprefixer-rails](https://github.com/ai/autoprefixer-rails) from 10.4.13.0 to 10.4.15.0.
- [Changelog](https://github.com/ai/autoprefixer-rails/blob/master/CHANGELOG.md)
- [Commits](ai/autoprefixer-rails@10.4.13.0...10.4.15.0)

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

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

Gemfile.lock

@@ -9,7 +9,7 @@ GEM
       console (~> 1.10)
       io-event (~> 1.1)
       timers (~> 4.1)
-    autoprefixer-rails (10.4.13.0)
+    autoprefixer-rails (10.4.15.0)
       execjs (~> 2)
     colorator (1.1.0)
     concurrent-ruby (1.2.2)