Bump test-clients to 0.12.0 (strimzi#12038)

Signed-off-by: Lukas Kral <lukywill16@gmail.com>

Author: im-konge

systemtest/src/main/java/io/strimzi/systemtest/Environment.java

@@ -194,8 +194,8 @@ public class Environment {
     private static final String RESOURCE_ALLOCATION_STRATEGY_DEFAULT = "SHARE_MEMORY_FOR_ALL_COMPONENTS";
 
     private static final String ST_KAFKA_VERSION_DEFAULT = TestKafkaVersion.getDefaultSupportedKafkaVersion();
-    private static final String ST_CLIENTS_KAFKA_VERSION_DEFAULT = "4.0.0";
-    public static final String TEST_CLIENTS_VERSION_DEFAULT = "0.11.0";
+    private static final String ST_CLIENTS_KAFKA_VERSION_DEFAULT = "4.1.0";
+    public static final String TEST_CLIENTS_VERSION_DEFAULT = "0.12.0";
     public static final String ST_FILE_PLUGIN_URL_DEFAULT = "https://repo1.maven.org/maven2/org/apache/kafka/connect-file/" + ST_KAFKA_VERSION_DEFAULT + "/connect-file-" + ST_KAFKA_VERSION_DEFAULT + ".jar";
 
     public static final String IP_FAMILY_DEFAULT = "ipv4";