Bump rubocop-rails from 2.6.0 to 2.8.0 (#14734)

Bumps [rubocop-rails](https://github.com/rubocop-hq/rubocop-rails) from 2.6.0 to 2.8.0.
- [Release notes](https://github.com/rubocop-hq/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop-rails/compare/v2.6.0...v2.8.0)

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

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

Gemfile

@@ -141,7 +141,7 @@ group :development do
   gem 'letter_opener_web', '~> 1.4'
   gem 'memory_profiler'
   gem 'rubocop', '~> 0.88', require: false
-  gem 'rubocop-rails', '~> 2.6', require: false
+  gem 'rubocop-rails', '~> 2.8', require: false
   gem 'brakeman', '~> 4.9', require: false
   gem 'bundler-audit', '~> 0.7', require: false
 

Gemfile.lock

@@ -355,7 +355,7 @@ GEM
     mimemagic (0.3.5)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
-    minitest (5.14.1)
+    minitest (5.14.2)
     msgpack (1.3.3)
     multi_json (1.15.0)
     multipart-post (2.1.1)
@@ -546,10 +546,10 @@ GEM
       unicode-display_width (>= 1.4.0, < 2.0)
     rubocop-ast (0.3.0)
       parser (>= 2.7.1.4)
-    rubocop-rails (2.6.0)
+    rubocop-rails (2.8.0)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
-      rubocop (>= 0.82.0)
+      rubocop (>= 0.87.0)
     ruby-progressbar (1.10.1)
     ruby-saml (1.11.0)
       nokogiri (>= 1.5.10)
@@ -779,7 +779,7 @@ DEPENDENCIES
   rspec-sidekiq (~> 3.1)
   rspec_junit_formatter (~> 0.4)
   rubocop (~> 0.88)
-  rubocop-rails (~> 2.6)
+  rubocop-rails (~> 2.8)
   ruby-progressbar (~> 1.10)
   sanitize (~> 5.2)
   sidekiq (~> 6.1)