Fix typo

Author: hugovk

Doc/whatsnew/3.15.rst

@@ -213,7 +213,7 @@ For example::
 
 The following standard library modules have been updated to accept
 :class:`!frozendict`: :mod:`copy`, :mod:`decimal`, :mod:`json`, :mod:`marshal`,
-:mod:`plist` (only for serialization), :mod:`pickle`, :mod:`pprint` and
+:mod:`plistlib` (only for serialization), :mod:`pickle`, :mod:`pprint` and
 :mod:`xml.etree.ElementTree`.
 
 :func:`eval` and :func:`exec` accept :class:`!frozendict` for *globals*, and