FIX documentation and NEWS of ThreadedHTTPServer. (GH-6207) (GH-6302)

(cherry picked from commit 79c3bab35cce55e6d175aff96a845bc6d932b203)

Co-authored-by: Julien Palard <julien@palard.fr>
diff --git a/Doc/library/http.server.rst b/Doc/library/http.server.rst
index 4fe46cb..278ae55 100644
--- a/Doc/library/http.server.rst
+++ b/Doc/library/http.server.rst
@@ -37,8 +37,11 @@
 
    This class is identical to HTTPServer but uses threads to handle
    requests by using the :class:`~socketserver.ThreadingMixin`. This
-   is usefull to handle web browsers pre-opening sockets, on which
-   :class:`HTTPServer` would wait indefinitly.
+   is useful to handle web browsers pre-opening sockets, on which
+   :class:`HTTPServer` would wait indefinitely.
+
+   .. versionadded:: 3.7
+
 
 The :class:`HTTPServer` and :class:`ThreadedHTTPServer` must be given
 a *RequestHandlerClass* on instantiation, of which this module