Remove messaging header normalization

Author: AlchemyDing

instrumentation/kafka/kafka-clients/kafka-clients-0.11/testing/src/main/java/io/opentelemetry/instrumentation/kafkaclients/common/v0_11/internal/KafkaClientBaseTest.java

@@ -264,10 +264,18 @@ protected static List<AttributeAssertion> processAttributes(
               MESSAGING_MESSAGE_BODY_SIZE, messageValue.getBytes(StandardCharsets.UTF_8).length));
     }
     if (testHeaders) {
-      assertions.add(
-          equalTo(
-              AttributeKey.stringArrayKey("messaging.header.Test-Message-Header"),
-              Collections.singletonList("test")));
+      if (SemconvStability.isEmitOldMessageSemconv()) {
+        assertions.add(
+            equalTo(
+                AttributeKey.stringArrayKey("messaging.header.Test_Message_Header"),
+                Collections.singletonList("test")));
+      }
+      if (SemconvStability.isEmitStableMessageSemconv()) {
+        assertions.add(
+            equalTo(
+                AttributeKey.stringArrayKey("messaging.header.Test-Message-Header"),
+                Collections.singletonList("test")));
+      }
     }
 
     if (testMultiBaggage) {