Update Kafka Connect base test plumbing

Author: trask

instrumentation/kafka/kafka-connect-2.6/testing/src/test/java/io/opentelemetry/instrumentation/kafkaconnect/v2_6/KafkaConnectSinkTaskBaseTest.java

@@ -275,6 +275,9 @@ private void setupKafkaConnect() {
             .withEnv("OTEL_BSP_MAX_EXPORT_BATCH_SIZE", "1")
             .withEnv("OTEL_BSP_SCHEDULE_DELAY", "10ms")
             .withEnv("OTEL_METRIC_EXPORT_INTERVAL", "1000")
+            .withEnv(
+                "OTEL_SEMCONV_STABILITY_OPT_IN",
+                System.getProperty("otel.semconv-stability.opt-in"))
             .withEnv("CONNECT_BOOTSTRAP_SERVERS", getInternalKafkaBoostrapServers())
             .withEnv("CONNECT_REST_ADVERTISED_HOST_NAME", KAFKA_CONNECT_NETWORK_ALIAS)
             .withEnv("CONNECT_PLUGIN_PATH", PLUGIN_PATH_CONTAINER)