Remove trailing whitespace

Author: mpdude

session.rst

@@ -267,7 +267,7 @@ needs.
 
 .. tip::
 
-    Accessing flash messages means that the session must be started, which 
+    Accessing flash messages means that the session must be started, which
     in turn will cause Symfony to mark the responses as ``private``. In general,
     since flashes shall displayed only once, pages that might display flashes
     cannot reasonably be cached in HTTP caches