refactor: Remove unnecessary comments regarding required fields in Group model

lib/data/models/group.dart

@@ -1,7 +1,7 @@
 import 'group_member.dart';
 
 class Group {
-  final String id; // ID obligatoire maintenant
+  final String id; 
   final String name;
   final String tripId;
   final String createdBy;
@@ -10,7 +10,7 @@ class Group {
   final List<GroupMember> members;
 
   Group({
-    required this.id, // Obligatoire
+    required this.id, 
     required this.name,
     required this.tripId,
     required this.createdBy,