Fix `javax.management.InstanceAlreadyExistsException` in tests

[nomisRev]

 javax.management.InstanceAlreadyExistsException: kafka.admin.client:type=app-info,id=test-kafka-admin-client
        at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:437)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerWithRepository(DefaultMBeanServerInterceptor.java:1898)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:966)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:900)
        at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:324)
        at com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:522)
        at org.apache.kafka.common.utils.AppInfoParser.registerAppInfo(AppInfoParser.java:64)
        at org.apache.kafka.clients.admin.KafkaAdminClient.<init>(KafkaAdminClient.java:602)
        at org.apache.kafka.clients.admin.KafkaAdminClient.createInternal(KafkaAdminClient.java:544)
        at org.apache.kafka.clients.admin.KafkaAdminClient.createInternal(KafkaAdminClient.java:488)
        at org.apache.kafka.clients.admin.Admin.create(Admin.java:134)
        at io.github.nomisRev.kafka.AdminKt.Admin(Admin.kt:43)
        at io.github.nomisrev.kafka.KafkaSpec.committedCount(KafkaSpec.kt:154)
        at io.github.nomisrev.kafka.consumer.KafakReceiverSpec$1$9$1.invokeSuspend(KafakReceiverSpec.kt:204)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.flow.internal.SafeCollector.invokeSuspend(SafeCollector.kt:48)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:750)