Fix highlight card displaying unpublished process

[Stef-Rousset]

🎩 What? Why?

This PR updates the menu_helper so that the process displayed in main-dropdown-menu is a published one.

📌 Related Issues

• Related to https://github.com/orgs/OpenSourcePolitics/projects/26/views/1?pane=issue&itemId=133646863&issue=OpenSourcePolitics%7Cintern-tasks%7C182
• Fixes Unpublish highlighted process still appears in main-dropdown-menu decidim/decidim#15364

Testing

1. As an admin, promote 2 processes in the BO
2. As a user, in the FO go to the index of processes, open the main-dropdown-menu and see which process appears as highlighted in the menu, let call it process one (screenshot one)
3. As an admin, unpublish process one (screenshot two)
4. Go back to the index of processes in the FO and see that process one is not displayed anymore, but the other promoted published process is displayed ((screenshot three)

📋 Subtasks

• Add tests

📷 Screenshots (optional)

ONE

TWO

THREE