Fix issue where project maintainers can not assign compliance frameworks

What does this MR do?

• Fixes the regression described in #321380 (closed).
• Reinstates the ability for maintainers to assign a compliance framework to a project by placing the upcoming policy change behind the feature flag.

	Before this MR	After this MR	Later, once feature flag is enabled
Lower than maintainer	❌	❌	❌
Maintainer	❌	✔	❌
Owner	✔	✔	✔

What happens if we don't merge this MR?

• Project maintainers cannot set a compliance framework for a project, despite the UI making it appear as though they can.

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

Related to #321380 (closed)