Remove redundant docstring

The method is quite simple and it doesn't need a dostring.
Also existing docstring was incorrect. The name of the expected
parameter is 'name', not 'node'. And it cannot be an object
of the type node.StorageNode

Change-Id: I94124d327c490d45eae4d2ded218beadfbc33ad7

watcher/decision_engine/model/model_root.py

@@ -391,10 +391,6 @@ class StorageModelRoot(nx.DiGraph, base.Model):
 
     @lockutils.synchronized("storage_model")
     def get_node_by_name(self, name):
-        """Get a node by node name
-
-        :param node: :py:class:`~.node.StorageNode` object or node name
-        """
         try:
             return self._get_by_name(name.split("#")[0])
         except exception.StorageResourceNotFound: