Prerequisite: Start with what we have

https://github.com/stolostron/rhacm-docs/blob/2.9_stage/applications/app_model.adoc

https://github.com/stolostron/rhacm-docs/blob/2.9_stage/gitops/gitops_overview.adoc

I have a suggested doc PR opened for this issue:

https://github.com/stolostron/rhacm-docs/pull/5476

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: 
       We created a new GitOps section for the doc to capture all the GitOps topics such as ACM application lifecycle Channel/Subscription model and ArgoCD/OpenShift-GitOps:

https://issues.redhat.com/browse/ACM-6039

https://issues.redhat.com/browse/ACM-6947

We added "maintenance" references for ACM app lifecycle Channel/Subscription model but we want to remove those references now because some customers are still heavily rely on the channel/subscription model for application delivery.

I am suggesting we make the following change:

https://github.com/stolostron/rhacm-docs/pull/5476
            
       - [NA] Add Required access level for the user to complete the task here:
       

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