Drop license_management artifact [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Drop drop_license_management_artifact feature flag as well as license_management artifact itself and it's usage.

We need to drop license_management artifact type as well because tests are highly coupled on the list of available types. Also, that's a good thing for the codebase as right now it's quite confusing to see license_management in the list of supported artifacts, where in fact, we don't support it since 13.0

We dropped support for license_management in 13.0 and since then we don't create such artifacts and don't store them. We also finished migration of existing license_management artifacts to license_scanning so we don't have them in the database.

So this is a safe step to remove license_management from the list of artifact types.

This MR can be separated into smaller ones as this is a breaking change.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• [-] 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

Related to #299114 (closed)