[3.8] Added missing coma after end of list in subprocess.rst (GH-17389)

(cherry picked from commit f25875a)

Author: Seluj78

Doc/library/subprocess.rst

@@ -596,7 +596,7 @@ functions.
 
       Popen and the other functions in this module that use it raise an
       :ref:`auditing event <auditing>` ``subprocess.Popen`` with arguments
-      ``executable``, ``args``, ``cwd``, ``env``. The value for ``args``
+      ``executable``, ``args``, ``cwd``, and ``env``. The value for ``args``
       may be a single string or a list of strings, depending on platform.
 
    .. versionchanged:: 3.2