Bump rubocop-rails from 2.15.2 to 2.24.1

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.15.2 to 2.24.1.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rails@v2.15.2...v2.24.1)

---
updated-dependencies:
- dependency-name: rubocop-rails
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -298,10 +298,11 @@ GEM
     rubocop-performance (1.19.1)
       rubocop (>= 1.7.0, < 2.0)
       rubocop-ast (>= 0.4.0)
-    rubocop-rails (2.15.2)
+    rubocop-rails (2.24.1)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
-      rubocop (>= 1.7.0, < 2.0)
+      rubocop (>= 1.33.0, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
     sassc (2.4.0)