Bump rails_admin from 3.1.3 to 3.1.4

Bumps [rails_admin](https://github.com/sferik/rails_admin) from 3.1.3 to 3.1.4.
- [Changelog](https://github.com/railsadminteam/rails_admin/blob/v3.1.4/CHANGELOG.md)
- [Commits](https://github.com/sferik/rails_admin/compare/v3.1.3...v3.1.4)

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

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

Gemfile.lock

@@ -374,7 +374,7 @@ GEM
     rails-timeago (2.20.0)
       actionpack (>= 5.2)
       activesupport (>= 5.2)
-    rails_admin (3.1.3)
+    rails_admin (3.1.4)
       activemodel-serializers-xml (>= 1.0)
       kaminari (>= 0.14, < 2.0)
       nested_form (~> 0.3)