Cluster Explorer side nav should not auto-collapse

[catherineluse]

This issue is related to a larger issue https://github.com/rancher/dashboard/issues/4431 which still in design triage, but after discussion with Kenneth and based on feedback from customers (https://github.com/rancher/dashboard/issues/4431#issuecomment-1064318705) it sounds like we definitely want to do at least this small piece of it.