Fix incorrect indentation on 'versionadded' for weakref.ref.__callback__.
diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst
index 78ff21d0..ec50107 100644
--- a/Doc/library/weakref.rst
+++ b/Doc/library/weakref.rst
@@ -117,8 +117,8 @@
weakref. If there is no callback or if the referent of the weakref is
no longer alive then this attribute will have value ``None``.
- .. versionadded:: 3.4
- Added the :attr:`__callback__` attribute.
+ .. versionadded:: 3.4
+ Added the :attr:`__callback__` attribute.
.. function:: proxy(object[, callback])