fix ndjsonserialization issue (Azure#21011)

Author: kryalama

sdk/monitor/azure-monitor-opentelemetry-exporter/src/main/java/com/azure/monitor/opentelemetry/exporter/AzureMonitorExporterBuilder.java

@@ -227,8 +227,8 @@ MonitorExporterAsyncClient buildAsyncClient() {
         // Customize serializer to use NDJSON
         final SimpleModule ndjsonModule = new SimpleModule("Ndjson List Serializer");
         JacksonAdapter jacksonAdapter = new JacksonAdapter();
-        jacksonAdapter.serializer().registerModule(ndjsonModule);
         ndjsonModule.addSerializer(new NdJsonSerializer());
+        jacksonAdapter.serializer().registerModule(ndjsonModule);
         restServiceClientBuilder.serializerAdapter(jacksonAdapter);
         ApplicationInsightsClientImpl restServiceClient = restServiceClientBuilder.buildClient();