Use standard heading for ast module docs
diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst
index ef36f50..d9b2212 100644
--- a/Doc/library/ast.rst
+++ b/Doc/library/ast.rst
@@ -1,7 +1,5 @@
-.. _ast:
-
-Abstract Syntax Trees
-=====================
+:mod:`ast` --- Abstract Syntax Trees
+====================================
 
 .. module:: ast
    :synopsis: Abstract Syntax Tree classes and manipulation.