Clarify that named tuples do not have to subclass tuple.

git-svn-id: http://svn.python.org/projects/python/trunk@69276 6015fed2-1504-0410-9fe1-9d1591cc4771

Author: raymond.hettinger

Doc/glossary.rst

@@ -396,7 +396,7 @@ Glossary
       also :term:`immutable`.
 
    named tuple
-      Any tuple subclass whose indexable elements are also accessible using
+      Any tuple-like class whose indexable elements are also accessible using
       named attributes (for example, :func:`time.localtime` returns a
       tuple-like object where the *year* is accessible either with an
       index such as ``t[0]`` or with a named attribute like ``t.tm_year``).