Bump rubocop-rails from 2.20.2 to 2.21.0

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.20.2 to 2.21.0.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rails/compare/v2.20.2...v2.21.0)

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

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

Gemfile

@@ -92,7 +92,7 @@ group :development, :test do
   gem "rspec-rails", "~> 6.0"
   gem "rspec-sidekiq", "~> 4.0", require: false
   gem "rubocop", "~> 1.56"
-  gem "rubocop-rails", "~> 2.20"
+  gem "rubocop-rails", "~> 2.21"
   gem "shoulda-matchers", "~> 5.3"
   gem "simplecov", require: false
   gem "simplecov-cobertura", require: false

Gemfile.lock

@@ -253,7 +253,7 @@ GEM
     mini_magick (4.12.0)
     mini_mime (1.1.5)
     mini_portile2 (2.8.4)
-    minitest (5.19.0)
+    minitest (5.20.0)
     msgpack (1.6.0)
     multi_json (1.15.0)
     multi_xml (0.6.0)
@@ -404,7 +404,7 @@ GEM
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.29.0)
       parser (>= 3.2.1.0)
-    rubocop-rails (2.20.2)
+    rubocop-rails (2.21.0)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.33.0, < 2.0)
@@ -556,7 +556,7 @@ DEPENDENCIES
   rspec-rails (~> 6.0)
   rspec-sidekiq (~> 4.0)
   rubocop (~> 1.56)
-  rubocop-rails (~> 2.20)
+  rubocop-rails (~> 2.21)
   rubyzip (~> 2.3)
   sanitize
   sassc-rails