Bump slim-rails from 3.4.0 to 3.5.1

Bumps [slim-rails](https://github.com/slim-template/slim-rails) from 3.4.0 to 3.5.1.
- [Release notes](https://github.com/slim-template/slim-rails/releases)
- [Changelog](https://github.com/slim-template/slim-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/slim-template/slim-rails/compare/v3.4.0...v3.5.1)

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

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

Gemfile.lock

@@ -454,7 +454,7 @@ GEM
     slim (4.1.0)
       temple (>= 0.7.6, < 0.9)
       tilt (>= 2.0.6, < 2.1)
-    slim-rails (3.4.0)
+    slim-rails (3.5.1)
       actionpack (>= 3.1)
       railties (>= 3.1)
       slim (>= 3.0, < 5.0)