Bump rubocop-factory_bot from 2.26.1 to 2.27.1

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

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

---
updated-dependencies:
- dependency-name: rubocop-factory_bot
  dependency-version: 2.27.1
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

.rubocop.yml

@@ -1,6 +1,7 @@
+plugins:
+  - rubocop-factory_bot
 require:
   - rubocop-capybara
-  - rubocop-factory_bot
   - rubocop-performance
   - rubocop-rails
   - rubocop-rspec