Update rubocop-rails requirement from = 2.20.2 to = 2.21.1 (#113)

Updates the requirements on [rubocop-rails](https://github.com/rubocop/rubocop-rails) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rails@v2.20.2...v2.21.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -5,7 +5,7 @@ PATH
       rubocop (= 1.56.3)
       rubocop-faker (= 1.1.0)
       rubocop-performance (= 1.19.1)
-      rubocop-rails (= 2.20.2)
+      rubocop-rails (= 2.21.1)
       rubocop-rake (= 0.6.0)
       rubocop-rspec (= 2.24.0)
 
@@ -199,7 +199,7 @@ GEM
     rubocop-performance (1.19.1)
       rubocop (>= 1.7.0, < 2.0)
       rubocop-ast (>= 0.4.0)
-    rubocop-rails (2.20.2)
+    rubocop-rails (2.21.1)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.33.0, < 2.0)

boxt_rubocop.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "rubocop", "1.56.3"
   spec.add_dependency "rubocop-faker", "1.1.0"
   spec.add_dependency "rubocop-performance", "1.19.1"
-  spec.add_dependency "rubocop-rails", "2.20.2"
+  spec.add_dependency "rubocop-rails", "2.21.1"
   spec.add_dependency "rubocop-rake", "0.6.0"
   spec.add_dependency "rubocop-rspec", "2.24.0"
 end