pystencils_walberla: don't sort members

they are in the same order as the kernel arguments, which is ordered in some way already

python/pystencils_walberla/jinja_filters.py

@@ -365,7 +365,7 @@ def generate_members(ctx, kernel_info, parameters_to_ignore=(), only_fields=Fals
     if hasattr(kernel_info, 'varying_parameters'):
         result.extend(["%s %s_;" % e for e in kernel_info.varying_parameters])
 
-    return "\n".join(sorted(result))
+    return "\n".join(result)
 
 
 def generate_destructor(kernel_info, class_name):