Fix: update guest_meeting to fix registration form

[Stef-Rousset]

🎩 Description

This PR bumps guest_meeting_registration module to its latest commit to fix a bug in the registration form.
It also bumps the decidim-module-ai to 0.31.5 to fix an error.

Testing

1. As an admin, create an upcoming meeting with registration on the platform.
2. Go then to the registrations, check the "Registrations enabled", "Registration form enabled" and "Allow unregistered users to join meetings".
3. Click on registration form button to add a registration form
4. Then add a question, a separator and a second question.
5. As a non logged_in user, go to the meeting, and click on "Join the meeting" and then "Register as guest".
6. See that the registration form is well displayed with its 2 steps (cf screenshots)

📌 Related Issues

Link your PR to an issue

• Fixes https://github.com/orgs/OpenSourcePolitics/projects/26/views/1?pane=issue&itemId=184881316&issue=OpenSourcePolitics%7Cintern-tasks%7C442

📷 Screenshots

[Stef-Rousset]

The failing test will be fixed when PR decidim/decidim#16879 will be merged in 0.30.