update php-cs-fixer and rector + fix rules

rector.php

@@ -50,9 +50,6 @@ return static function (RectorConfig $rectorConfig): void {
 
     // skip some path...
     $rectorConfig->skip([
-        // we need to discuss this: are we going to have FALSE in tests instead of an error ?
-        \Rector\Php71\Rector\FuncCall\CountOnNullRector::class,
-
         // we must adapt service definition
         \Rector\Symfony\Symfony28\Rector\MethodCall\GetToConstructorInjectionRector::class,
         \Rector\Symfony\Symfony34\Rector\Closure\ContainerGetNameToTypeInTestsRector::class,