[3.15] gh-86726: Fix "deprecated" directive for wm_attributes (GH-151652) (GH-151654)

(cherry picked from commit d47c27e)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Author: miss-islington

Doc/library/tkinter.rst

@@ -2458,7 +2458,7 @@ Base and mixin classes
          ``-``, and attributes may be set using keyword arguments.
          The *return_python_dict* parameter was added.
 
-      .. deprecated:: next
+      .. deprecated:: 3.13
          Setting an attribute by passing the option name (with a leading
          ``-``) and its value as two positional arguments, as in
          ``w.attributes('-alpha', 0.5)``, is deprecated; use keyword arguments