Update whatsnew/3.4.rst wrt. the socket constants switch to IntEnum

[issue #18730]
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
index 311c683..218b822 100644
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -320,6 +320,9 @@
 
 * :meth:`socket.socket.get_inheritable`, :meth:`socket.socket.set_inheritable`
 
+The ``socket.AF_*`` and ``socket.SOCK_*`` constants are enumeration values,
+using the new :mod:`enum` module. This allows descriptive reporting during
+debugging, instead of seeing integer "magic numbers".
 
 ssl
 ---