Disabled unused private elements detection

This inspection can't currently detect callbacks like `[$this, 'foo']`,
where `foo` is a `private` method of `$this` (slevomat/coding-standard#413).

Author: Ocramius

phpcs.xml.dist

@@ -17,6 +17,7 @@
     <file>./test/unit</file>
 
     <rule ref="Doctrine">
+        <exclude name="SlevomatCodingStandard.Classes.UnusedPrivateElements"/>
         <exclude-pattern>src/DetectChanges/BCBreak/InterfaceBased/InterfaceBased.php</exclude-pattern>
         <exclude-pattern>test/unit/Formatter/ReflectionFunctionAbstractNameTest.php</exclude-pattern>
         <exclude-pattern>test/unit/DetectChanges/BCBreak/FunctionBased/ParameterByReferenceChangedTest.php</exclude-pattern>