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>

.rubocop.yml

@@ -2,9 +2,9 @@ plugins:
   - rubocop-capybara
   - rubocop-factory_bot
   - rubocop-performance
+  - rubocop-rails
   - rubocop-rspec
 require:
-  - rubocop-rails
   - rubocop-rspec_rails
 
 AllCops: