Bump rubocop-rails from 2.29.1 to 2.33.4

We're changing the `.rubocop.yml` file because we were getting a
warning:

```
rubocop-rails extension supports plugin, specify `plugins:
rubocop-rails` instead of `require: rubocop-rails` in .rubocop.yml. For
more information, see
https://docs.rubocop.org/rubocop/plugin_migration_guide.html.
```

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.29.1 to 2.33.4.
- [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/v2.29.1...v2.33.4)

---
updated-dependencies:
- dependency-name: rubocop-rails
  dependency-version: 2.33.4
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Gemfile

@@ -107,7 +107,7 @@ group :development do
   gem "rubocop-capybara", "~> 2.22.1", require: false
   gem "rubocop-factory_bot", "~> 2.27.1", require: false
   gem "rubocop-performance", "~> 1.26.1", require: false
-  gem "rubocop-rails", "~> 2.29.1", require: false
+  gem "rubocop-rails", "~> 2.33.4", require: false
   gem "rubocop-rspec", "~> 3.7.0", require: false
   gem "rubocop-rspec_rails", "~> 2.30.0", require: false
   gem "rvm1-capistrano3", "~> 1.4.0", require: false