Remove feature flag from vulnerability GQL fields

What does this MR do?

Since the feature flag can't be scoped to a specific project, it's making it hard to test this feature in production. Removing the flag will allow us to test the fields and it's been decided that it's okay for customers to begin consuming the fields.

Issue: #215568 (closed)

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.