Remove trailing whitespace.
diff --git a/Doc/library/difflib.rst b/Doc/library/difflib.rst
index f19156d..addd813 100644
--- a/Doc/library/difflib.rst
+++ b/Doc/library/difflib.rst
@@ -428,7 +428,7 @@
 
       .. XXX Explain why a dummy is used!
 
-      .. versionchanged:: 2.5 
+      .. versionchanged:: 2.5
          The guarantee that adjacent triples always describe non-adjacent blocks
          was implemented.