Fix issue due to incompatible code on newer versions

Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/api/projects.rb

@@ -373,7 +373,7 @@ module API
         authorize! :admin_project, user_project
         required_attributes! [:group_id, :group_access]
 
-        group = Group.find_by_id(attrs[:group_id])
+        group = Group.find_by_id(params[:group_id])
 
         unless group && can?(current_user, :read_group, group)
           not_found!('Group')