minor #14933 [ExpressionLanguage][Security] Mention the "subject" expression language variable (javiereguiluz)

This PR was merged into the 4.4 branch.

Discussion
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[ExpressionLanguage][Security] Mention the "subject" expression language variable

This was requested in symfony/symfony#40089

By the way, in my opinion providing two different ways of doing exactly the same is always confusing.

Commits
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4511683 Mention the "subject" expression language variable

Author: OskarStark

security/expressions.rst

@@ -48,6 +48,8 @@ Inside the expression, you have access to a number of variables:
     does not include the ``IS_AUTHENTICATED_*`` attributes (see the functions below).
 ``object``
     The object (if any) that's passed as the second argument to ``isGranted()``.
+``subject``
+    It stores the same value as ``object``, so they are equivalent.
 ``token``
     The token object.
 ``trust_resolver``