Create an informative issue (See each section, incomplete templates/issues won't be triaged)

Using the current documentation as a model, please complete the issue template. 

Note: Doc team updates the current version and the two previous versions (n-2). For earlier versions, we will address only high-priority, customer-reported issues for releases in support.

Prerequisite: Start with what we have

Always look at the current documentation to describe the change that is needed. Use the source or portal link for Step 4:

 - Use the Customer Portal: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes

 - Use the GitHub link to find the staged docs in the repository: https://github.com/stolostron/rhacm-docs 

Describe the changes in the doc and link to your dev story

Provide info for the following steps:

1. - [x] Mandatory Add the required version to the Fix version/s field.

2. - [ ] Mandatory Choose the type of documentation change.

      - [ ] New topic in an existing section or new section
      - [x] Update to an existing topic

3. - [x] Mandatory for GA content:
            
       - [x] Add steps and/or other important conceptual information here: 

From 2.9 onwards it is required to use a label in the user-defined ACM hub cluster namespace: the label `openshift.io/cluster-monitoring: "true"` will cause Cluster Monitoring Operator to scrape a namespace

            
       - [ ] Add Required access level for the user to complete the task here:
       

       - [ ] Add verification at the end of the task, how does the user verify success (a command to run or a result to see?)
     
     
       - [ ] Add link to dev story here:

4. - [x] Mandatory for bugs: What is the diff? Clearly define what the problem is, what the change is, and link to the current documentation:

https://issues.redhat.com/browse/ACM-7631

https://issues.redhat.com/browse/ACM-7634

Previously, RHACM components including Observability created ServiceMonitors and PrometheusRule resources directly in openshift-monitoring namespace. This causes problems when trying to deploy RHACM in managed openshift scenarios as customers do not have permissions to write to openshift-monitoring namespace. 
From 2.9 onwards it is required to use a label in the user-defined ACM hub cluster namespace: the label `openshift.io/cluster-monitoring: "true"` will cause Cluster Monitoring Operator to scrape a namespace.

As a result of this change RHACM Observability ServiceMonitors and PrometheusRule resources are no longer present in openshift-monitoring namespace after RHACM 2.9 is deployed or an installation is upgraded to to ACM 2.9 from previous versions.