minor symfony#6899 Update access_control.rst (asandjivy)

This PR was submitted for the 3.1 branch but it was merged into the 2.7 branch instead (closes symfony#6899).

Discussion
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Update access_control.rst

The correct keyword is "roles"

Commits
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7c35e0c Update access_control.rst

Author: wouterj

security/access_control.rst

@@ -131,7 +131,7 @@ Once Symfony has decided which ``access_control`` entry matches (if any),
 it then *enforces* access restrictions based on the ``roles``, ``allow_if`` and ``requires_channel``
 options:
 
-* ``role`` If the user does not have the given role(s), then access is denied
+* ``roles`` If the user does not have the given role(s), then access is denied
   (internally, an :class:`Symfony\\Component\\Security\\Core\\Exception\\AccessDeniedException`
   is thrown);