Add versionchanged

Author: srittau

Doc/library/hashlib.rst

@@ -304,6 +304,10 @@ a file or file-like object.
 
    .. versionadded:: 3.11
 
+   .. versionchanged:: next
+      Now raises a :exc:`BlockingIOError` if the file is opened in blocking
+      mode. Previously, spurious null bytes were added to the digest.
+
 
 Key derivation
 --------------