build(deps-dev): bump rubocop-rails from 2.20.2 to 2.21.1

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.20.2 to 2.21.1.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rails@v2.20.2...v2.21.1)

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

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

Gemfile

@@ -28,7 +28,7 @@ group :development do
   gem "letter_opener", "~> 1.7"
   gem 'rubocop', '~> 1.56'
   gem 'rubocop-performance', '~> 1.19', require: false
-  gem 'rubocop-rails', '~> 2.20', require: false
+  gem 'rubocop-rails', '~> 2.21', require: false
   gem 'web-console', '~> 4.2'
 end
 

Gemfile.lock

@@ -239,7 +239,7 @@ GEM
     rubocop-performance (1.19.0)
       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)
@@ -318,7 +318,7 @@ DEPENDENCIES
   rollbar (~> 3.4)
   rubocop (~> 1.56)
   rubocop-performance (~> 1.19)
-  rubocop-rails (~> 2.20)
+  rubocop-rails (~> 2.21)
   sassc-rails (~> 2.1.2)
   selenium-webdriver (~> 4.12)
   serviceworker-rails (~> 0.6)