Link to risks of enabling disabled FFs in FF API docs

What does this MR do and why?

This merge request introduces a warning ⚠ and a link 🔗 to the Feature Flag API documentation to inform users of potential stability and security risks associated with enabling disabled feature flags. The intention is to raise user awareness and promote cautious decision-making when using features under development in production environments. By referring to the linked documentation, admins can gauge the risks and make informed choices based on their risk tolerance. 📚💡

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related issue: #410040 (closed)