Improve notes on enabling the secure_security_and_compliance_configuration_page_on_ce feature flag

What does this MR do?

Through working on a 🎫, we confirmed on 3x GitLab instances that the syntax for enabling the secure_security_and_compliance_configuration_page_on_ce feature flag in the docs requires a slight improvement.

GitLab team members with access to ZenDesk can learn more in the ticket. 🎫

Thank you @lkorbasiewicz!

The docs suggest:

Feature.enable(:secure_security_and_compliance_configuration_page_on_ce, Project.find(<project id>))

This did not lead to the desired effect. Instead, the following did:

Feature.enable(:secure_security_and_compliance_configuration_page_on_ce)

Screenshots (strongly suggested)

Once I had used the syntax shown above, I was able to see the Configuration area:

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is a small improvement to guidelines on setting a feature flag.
• 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