Description of problem:

The CAPA (Cluster API Provider AWS) ROSAControlPlane resource currently only applies the channelGroup field during cluster creation (day-1) and does not reconcile changes to this field for existing clusters (day-2 operations).

Version-Release number of selected component (if applicable): 

How reproducible:

Steps to Reproduce:

1. Users set spec.channelGroup: candidate in their ROSAControlPlane manifest as day 2 operation
2.  If users change spec.channelGroup in the manifest (e.g., from stable to candidate), CAPA does not reconcile this change
3.  

Actual results:

1. The actual cluster remains on the original channel group, despite the manifest showing the desired state

Expected results:

CAPA should reconcile channelGroup changes by:

1. Detecting when spec.channelGroup differs from the actual cluster configuration
2. Calling the appropriate OCM/ROSA APIs to update the cluster's channel group
3. Updating the ROSAControlPlane status to reflect the reconciliation progress

Additional info:

https://github.com/kubernetes-sigs/cluster-api-provider-aws/blob/main/controlplane/rosa/controllers/rosacontrolplane_controller.go#L501

Workaround is to manually switched the channel using the ROSA CLI

rosa edit cluster -c my-cluster --channel-group candidate