InteractiveShell.run_code: Update docstring.

The docstring refers to a post_execute parameter which was moved to the
class level in 54e4e463.

IPython/core/interactiveshell.py

@@ -2587,8 +2587,6 b' class InteractiveShell(SingletonConfigurable, Magic):'
         ----------
         code_obj : code object
           A compiled code object, to be executed
-        post_execute : bool [default: True]
-          whether to call post_execute hooks after this particular execution.
 
         Returns
         -------