Fix a tiny typo regarding save_handler type in Checkpoint class

ignite/handlers/checkpoint.py

@@ -82,7 +82,7 @@ class Checkpoint(Serializable):
             ``load_state_dict`` methods. If contains objects of type torch `DistributedDataParallel`_ or
             `DataParallel`_, their internal wrapped model is automatically saved (to avoid additional key ``module.`` in
             the state dictionary).
-        save_handler: String, method or callable class
+        save_handler: String, function or callable object.
             used to save engine and other provided objects. Function receives two objects: checkpoint as a dictionary
             and filename. If ``save_handler`` is callable class, it can
             inherit of :class:`~ignite.handlers.checkpoint.BaseSaveHandler` and optionally implement ``remove`` method