[Docs] Missing task 3.x coordinates in ref guide

[onobc]

We added the coordinates for the Spring Boot 3.x based stream applications here. We need to add the coordinates for the Spring Cloud Task 3.x and Spring Cloud Batch 5.x task apps as well.

The 3.x based task apps live here:

• https://repo.spring.io/artifactory/milestone/io/spring/timestamp-task/3.0.0/timestamp-task-3.0.0.jar
• https://repo.spring.io/artifactory/milestone/io/spring/timestamp-batch-task/3.0.0/timestamp-batch-task-3.0.0.jar

Register task apps w/ the following properties:

task.timestamp=maven://io.spring:timestamp-task:3.0.0
task.timestamp.bootVersion=3

task.timestamp-batch=maven://io.spring:timestamp-batch-task:3.0.0
task.timestamp-batch.bootVersion=3

For reference on the 2.x coordinates - they are talked about here.