minor #8114 incorrect session short description (tobemedia)

This PR was submitted for the 3.3 branch but it was merged into the 2.7 branch instead (closes #8114).

Discussion
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incorrect session short description

The session cookie only holds the session token. By default, the data attributes are stored (inside a bag) at a file.
@see NativeFileSessionHandler.

Commits
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4de0103 incorrect session short description

Author: weaverryan

controller.rst

@@ -352,8 +352,8 @@ Managing the Session
 --------------------
 
 Symfony provides a nice session object that you can use to store information
-about the user between requests. By default, Symfony stores the attributes in a
-cookie by using native PHP sessions.
+about the user between requests. By default, Symfony stores the token in a
+cookie and writes the attributes to a file by using native PHP sessions.
 
 To retrieve the session, call
 :method:`Symfony\\Bundle\\FrameworkBundle\\Controller\\Controller::getSession`