fix: migrate from deprecated annotate gem to annotaterb (#12845)

## Description

The `annotate` gem has been deprecated and users are experiencing
annotation errors with the new Rails 7 `serialize` syntax. This PR
migrates to `annotaterb`, the actively maintained fork.

Users reported errors when running `make db`:
```
Unable to annotate app/models/installation_config.rb: no implicit conversion of Hash into String  
Unable to annotate app/models/installation_config.rb: no implicit conversion of nil into Array
```

This PR updates the Gemfile and rake configuration to use `annotaterb`
instead.

Fixes #11673

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

Tested locally with the following steps:
1. Run `bundle install` - successfully installed annotaterb 4.20.0
2. Run `RAILS_ENV=development bundle exec rails db:chatwoot_prepare` -
completed without annotation errors
3. Run `RAILS_ENV=development bundle exec rails annotate_rb:models` -
successfully annotated all models including InstallationConfig
4. Verified InstallationConfig model annotations are present and correct

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] My changes generate no new warnings
- [x] New and existing unit tests pass locally with my changes

Gemfile

@@ -207,7 +207,7 @@ group :production do
 end
 
 group :development do
-  gem 'annotate'
+  gem 'annotaterb'
   gem 'bullet'
   gem 'letter_opener'
   gem 'scss_lint', require: false