Fix RFMF link in costs section

Updated RFMF link to use the correct URL.

Author: yguitton

W4E/w4e2026.qmd

@@ -19,7 +19,7 @@ For this new session, format changed:
 The pre-registration for the school is now open ! [Follow the link to pre-register](https://sondages.inrae.fr/index.php/576765?lang=fr).
 :::
 
-**Costs**: 1300€ for academic and 2500 € for private institution (to cover expenses for trainers, organization, materials and meals). A special discount of 100€ is offered for [RFMF](https://rfmf.fr) members 2025.
+**Costs**: 1300€ for academic and 2500 € for private institution (to cover expenses for trainers, organization, materials and meals). A special discount of 100€ is offered for [RFMF](https://www.rfmf.fr/) members 2025.
 
 **Invited speaker**:\
 To be defined