chore: Remove using

Author: HofmeisterAn

src/Testcontainers.Kafka/ApacheConfiguration.cs

@@ -52,7 +52,7 @@ public override string CreateStartupScript(KafkaConfiguration resourceConfigurat
     {
         var additionalAdvertisedListeners = string.Join(",", container.AdvertisedListeners ?? Array.Empty<string>());
 
-        using var startupScript = new StringWriter();
+        var startupScript = new StringWriter();
         startupScript.NewLine = "\n";
         startupScript.WriteLine("#!/bin/bash");
         startupScript.WriteLine("export KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://" + container.Hostname + ":" + container.GetMappedPublicPort(KafkaBuilder.KafkaPort) + ",BROKER://" + container.IpAddress + ":" + KafkaBuilder.BrokerPort + "," + additionalAdvertisedListeners);

src/Testcontainers.Kafka/ConfluentConfiguration.cs

@@ -55,7 +55,7 @@ public override string CreateStartupScript(KafkaConfiguration resourceConfigurat
 
         var hasLocalZooKeeper = isZooKeeperConsensus && resourceConfiguration.Environments.TryGetValue("KAFKA_ZOOKEEPER_CONNECT", out var connectionString) && connectionString.StartsWith("localhost");
 
-        using var startupScript = new StringWriter();
+        var startupScript = new StringWriter();
         startupScript.NewLine = "\n";
         startupScript.WriteLine("#!/bin/bash");