minor #6105 Removed deprecated methods from VoterInterface (edefimov)

This PR was merged into the 3.0 branch.

Discussion
----------

Removed deprecated methods from VoterInterface

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 3.0
| Fixed tickets |

This PR removes methods _supportsAttribute_, _supportsClass_ from _VoterInterface_ documentation

Commits
-------

874c840 Removed deprecated methods from VoterInterface

components/security/authorization.rst

@@ -85,25 +85,12 @@ of :class:`Symfony\\Component\\Security\\Core\\Authorization\\Voter\\VoterInterf
 which means they have to implement a few methods which allows the decision
 manager to use them:
 
-``supportsAttribute($attribute)`` (deprecated as of 2.8)
-    will be used to check if the voter knows how to handle the given attribute;
-
-``supportsClass($class)`` (deprecated as of 2.8)
-    will be used to check if the voter is able to grant or deny access for
-    an object of the given class;
-
 ``vote(TokenInterface $token, $object, array $attributes)``
     this method will do the actual voting and return a value equal to one
     of the class constants of :class:`Symfony\\Component\\Security\\Core\\Authorization\\Voter\\VoterInterface`,
     i.e. ``VoterInterface::ACCESS_GRANTED``, ``VoterInterface::ACCESS_DENIED``
     or ``VoterInterface::ACCESS_ABSTAIN``;
 
-.. note::
-
-    The ``supportsAttribute()`` and ``supportsClass()`` methods are deprecated
-    as of Symfony 2.8 and no longer required in 3.0. These methods should not
-    be called outside the voter class.
-
 The Security component contains some standard voters which cover many use
 cases: