bpo-19698: Document when importlib.machinery.FrozenImporter gained spec-related methods (GH-19158) (GH-19165)

(cherry picked from commit 302e5a8)

Co-authored-by: Brett Cannon <54418+brettcannon@users.noreply.github.com>

Co-authored-by: Brett Cannon <54418+brettcannon@users.noreply.github.com>

Author: miss-islington

Doc/library/importlib.rst

@@ -1029,6 +1029,10 @@ find and load modules.
     Only class methods are defined by this class to alleviate the need for
     instantiation.
 
+    .. versionchanged:: 3.4
+       Gained :meth:`~Loader.create_module` and :meth:`~Loader.exec_module`
+       methods.
+
 
 .. class:: WindowsRegistryFinder