Add section in docs about how to disable batch metrics

Related to https://github.com/spring-projects/spring-batch/issues/3677#issuecomment-601157948, the documentation should be updated to include a note about how to disable batch metrics reported by micrometer. The new section should be added in [Monitoring and metrics](https://docs.spring.io/spring-batch/docs/4.2.x/reference/html/monitoring-and-metrics.html#monitoring-and-metrics).