bpo-40204: Add :noindex: in the documentation (GH-21859)

Add :noindex: to duplicated documentation to fix "duplicate object
description" errors.

For example, fix this Sphinx 3 issue:

Doc/library/configparser.rst:1146: WARNING: duplicate object
description of configparser.ConfigParser.optionxform, other instance
in library/configparser, use :noindex: for one of them
diff --git a/Doc/library/token.rst b/Doc/library/token.rst
index f8ebb27..a1aceba 100644
--- a/Doc/library/token.rst
+++ b/Doc/library/token.rst
@@ -70,6 +70,7 @@
 
 
 .. data:: TYPE_COMMENT
+   :noindex:
 
    Token value indicating that a type comment was recognized.  Such
    tokens are only produced when :func:`ast.parse()` is invoked with