doc string typo fix

Author: jchanvfx

NodeGraphQt/base/graph.py

@@ -874,9 +874,9 @@ def acyclic(self):
         """
         return self._model.acyclic
 
-    def set_acyclic(self, mode=False):
+    def set_acyclic(self, mode=True):
         """
-        Enable the node graph to be a acyclic graph. (default: ``False``)
+        Enable the node graph to be a acyclic graph. (default: ``True``)
 
         See Also:
             :meth:`NodeGraph.acyclic`