Migrate confidential message to use PJ style class

What does this MR do and why?

In this MR, we update the ProjectFormGroup to use PJ style classes.

Screenshots or screen recordings

This does not introduce any UI/UX changes

How to set up and validate locally

1. Navigate to the issues page > select an issue
2. Click on the "Create merge request" button to trigger the dropdown
3. The description color remains the same as before

Before	After (this MR)

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.