Fix constant lookup issue for `Vulnerabilities::BaseService`

What does this MR do?

This MR fixes two issues;

1. The constant lookup issue for the Vulnerabilities::BaseService.

   For the environments which are configured to utilize Rails' autoloading feature, Vulnerabilities.const_get(:BaseService) is always resolving the Object::BaseService after the commit a53c0d24. The reason is, with the change in labels factory, we are loading the Object::BaseService into memory and Vulnerabilities.const_get(:BaseService) is not calling the const_missing method to initiate the process of loading the vulnerabilities/base_service.rb file. This was always a problem but became a permanent one with the aforementioned commit as we always load the ::BaseService into memory before loading any other service.

2. Unnecessary module import which is already imported by the superclass.

Screenshots

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

• [-] 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