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

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

Update to topic: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.9/html/business_continuity/business-cont-overview#volsync-install-clusters

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

See parent story: https://issues.redhat.com/browse/ACM-9951. (VolSync will start supporting N-1 releases only starting with upcoming v0.9.0 release).

This means users on older ACM releases may need to update their VolSync versions to a supported one (will be v0.8.z and v0.9.z as of ACM 2.10 release).

We have documentation already on using a volsync ManagedClusterAddOn  to install VolSync on managed clusters: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.9/html/business_continuity/business-cont-overview#volsync-install-mcaddon

Now though we should probably add something about VolSync support and we can add instructions on how to update the volsync ManagedClusterAddOn to choose what operator channel to use.

Users can add the following annotation to their ManagedClusterAddOn resources to set the operator channel that volsync should be deployed from on their managed cluster:

```

   annotations:
       operator-subscription-channel: stable-0.9

```

Adding the above annotation will instruct ACM to deploy volsync from the `stable-0.9` channel on the managed cluster.

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