[doc] Add missing backtick. (GH-32355)

Author: JulienPalard

Doc/whatsnew/3.11.rst

@@ -805,7 +805,7 @@ Deprecated
 * :class:`configparser.LegacyInterpolation` has been deprecated in the docstring
   since Python 3.2. It now emits a :exc:`DeprecationWarning` and will be removed
   in Python 3.13. Use :class:`configparser.BasicInterpolation` or
-  :class:`configparser.ExtendedInterpolation instead.
+  :class:`configparser.ExtendedInterpolation` instead.
   (Contributed by Hugo van Kemenade in :issue:`46607`.)
 
 * The :func:`locale.getdefaultlocale` function is deprecated and will be