Feat(subscription/new): hide EoA deprecated plans

What does this MR do?

This MR removes the bronze (deprecated) plan as an option for EoA when users are trying to start a new subscription.

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

To test this out:

• You need a group on a trial plan in order to see the new subscription flow

• Enable this feature flag: Feature.enable(:hide_deprecated_billing_plans)

• git apply this deprecate-bronze-subscription-plan.patch

• Navigate here: http://localhost:3000/-/subscriptions/new?namespace_id=28&plan_id=2c92c0f95a24621b015a259a50307881, or try subscribing to a new plan from one of your groups

• You should not see the bronze plan in the options of the dropdown

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

• Tested in all supported browsers

• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team