Update process to enable observability

What does this MR do and why?

This changes the process for enabling observability by relying on the automatic provisioning process.

References

Screenshots or screen recordings

Before	After
Screen_Recording_2025-10-15_at_4.53.46_PM	Screen_Recording_2025-10-10_at_5.56.03_PM

How to set up and validate locally

1. In a rails console enable the feature flag:

Feature.enable(:observability_sass_features, group)

2. Head to http://localhost:3000/groups/toolbox/-/observability/setup and view the page
3. In a rails console add the o11y setting:

   group = Group.find_by_path('toolbox')
   group.create_observability_group_o11y_setting!(
	  o11y_service_url: "http://localhost:8080",
	  o11y_service_user_email: 'fakeuser@gitlab.com',
	  o11y_service_password: "asupersecretpassword",
	  o11y_service_post_message_encryption_key: "your-super-secret-encryption-key-here-32-chars-minimum",
   )
4. Click on the `Enable Observability` button 
5. If you want to, clean up your o11y setting:
```ruby
group.observability_group_o11y_setting.destroy!

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.