Use 'callback parameter' instead of 'closure'.

Author: ZeroIntensity

peps/pep-0788.rst

@@ -924,17 +924,17 @@ deadlock the interpreter if it's not released.
         Py_RETURN_NONE;
     }
 
-Example: Calling Python Without a Closure
-*****************************************
+Example: Calling Python Without a Callback Parameter
+****************************************************
 
-There are a few cases where callback functions don't take a closure
+There are a few cases where callback functions don't take a callback parameter
 (``void *arg``), so it's impossible to acquire a reference to any specific
 interpreter. The solution to this problem is to acquire a reference to the main
 interpreter through :c:func:`PyInterpreterState_AsStrong`.
 
 But wait, won't that break with subinterpreters, per
 :ref:`pep-788-subinterpreters-gilstate`? Fortunately, since the callback has
-no closure, it's not possible for the caller to pass any objects or
+no callback parameter, it's not possible for the caller to pass any objects or
 interpreter-specific data, so it's completely safe to choose the main
 interpreter here.