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

Provide info for the following steps:

1. - [ ] 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

     https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.8/html/clusters/cluster_mce_overview#hibernating-a-created-cluster

     
       - [ ] 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:

In RHACM 2.9, we will REMOVE the Technology Preview disclaimer for the Cluster Hibernate feature.

https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.8/html/clusters/cluster_mce_overview#hibernating-a-created-cluster

Please note that the words Technology Preview are in the left side TOC, as well as the topic title.

We will also need to make the change into the MCE and ACM support matrices for 2.4/2.9