plugin (XEP-0059): fix max handling:

since the move to the new model, the `_` suffix must not be used any more with `max`.

libervia/backend/plugins/plugin_xep_0059.py

@@ -196,8 +196,7 @@ class XEP_0059:
         rsm_args = {}
         for arg in ("max", "after", "before", "index"):
             try:
-                argname = "max_" if arg == "max" else arg
-                rsm_args[argname] = extra.pop(f"{RSM_PREFIX}{arg}")
+                rsm_args[arg] = extra.pop(f"{RSM_PREFIX}{arg}")
             except KeyError:
                 continue