Remove outdated comment in Artist.__getstate__

Author: artemshekh

lib/matplotlib/artist.py

@@ -215,8 +215,6 @@ def __init__(self):
 
     def __getstate__(self):
         d = self.__dict__.copy()
-        # remove the unpicklable remove method, this will get re-added on load
-        # (by the Axes) if the artist lives on an Axes.
         d['stale_callback'] = None
         return d