Small __getstate__ cleanups.

Remove outdated comment in `AxesBase.__getstate__` (we don't cache the
renderer on it anymore).

Remove unnecessary `SubplotSpec.__getstate__` (it has become unnecessary
now that SubplotSpec doesn't hold onto layoutbox/poslayoutbox anymore.)

Author: anntzer

lib/matplotlib/axes/_base.py

@@ -682,8 +682,6 @@ def __init__(self, fig, rect,
             which='major')
 
     def __getstate__(self):
-        # The renderer should be re-created by the figure, and then cached at
-        # that point.
         state = super().__getstate__()
         # Prune the sharing & twinning info to only contain the current group.
         state["_shared_axes"] = {

lib/matplotlib/gridspec.py

@@ -623,9 +623,6 @@ def num2(self):
     def num2(self, value):
         self._num2 = value
 
-    def __getstate__(self):
-        return {**self.__dict__}
-
     def get_gridspec(self):
         return self._gridspec