Bump simplecov from 0.17.1 to 0.18.1 (#13027)

Bumps [simplecov](https://github.com/colszowka/simplecov) from 0.17.1 to 0.18.1.
- [Release notes](https://github.com/colszowka/simplecov/releases)
- [Changelog](https://github.com/colszowka/simplecov/blob/master/CHANGELOG.md)
- [Commits](https://github.com/colszowka/simplecov/compare/v0.17.1...v0.18.1)

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

Gemfile

@@ -124,7 +124,7 @@ group :test do
   gem 'microformats', '~> 4.2'
   gem 'rails-controller-testing', '~> 1.0'
   gem 'rspec-sidekiq', '~> 3.0'
-  gem 'simplecov', '~> 0.17', require: false
+  gem 'simplecov', '~> 0.18', require: false
   gem 'webmock', '~> 3.8'
   gem 'parallel_tests', '~> 2.30'
 end