add note about default protocol of spring boot starter

content/en/docs/languages/java/automatic/spring-boot.md

@@ -165,7 +165,16 @@ IDE.
 
 The OpenTelemetry Starter supports all the
 [SDK Autoconfiguration](/docs/languages/java/automatic/configuration/#sdk-autoconfiguration)
-(since 2.2.0). You can set properties in the `application.properties` or the
+(since 2.2.0). 
+
+{{% alert title="Attention" color="warning" %}}
+
+Unlike the SDK autoconfiguration, the OpenTelemetry Spring Boot starter uses `http/protobuf` as the default
+protocol, not `grpc`.
+
+{{% /alert %}}
+
+You can set properties in the `application.properties` or the
 `application.yaml` file, or use environment variables.
 
 `application.properties` example: