[Cache] Fix tests

Author: nicolas-grekas

src/Symfony/Component/Cache/Tests/Adapter/PredisClusterAdapterTest.php

@@ -21,9 +21,4 @@ public static function setUpBeforeClass(): void
         parent::setUpBeforeClass();
         self::$redis = new \Predis\Client(array_combine(['host', 'port'], explode(':', getenv('REDIS_HOST')) + [1 => 6379]), ['prefix' => 'prefix_']);
     }
-
-    public static function tearDownAfterClass(): void
-    {
-        self::$redis = null;
-    }
 }

src/Symfony/Component/Cache/Tests/Adapter/PredisRedisClusterAdapterTest.php

@@ -27,9 +27,4 @@ public static function setUpBeforeClass(): void
 
         self::$redis = RedisAdapter::createConnection('redis:?host['.str_replace(' ', ']&host[', $hosts).']', ['class' => \Predis\Client::class, 'redis_cluster' => true, 'prefix' => 'prefix_']);
     }
-
-    public static function tearDownAfterClass(): void
-    {
-        self::$redis = null;
-    }
 }