Render upgrade banner above ImpersonatingBanner

Editor assessment

The subject states the layout correction exactly: the upgrade banner renders above the ImpersonatingBanner, which names both components and their stacking order. fix is right, and the missing scope is tolerable since the components are named. No body or footer; the pull number gives provenance. Wording is compact and imperative. A complete message for a small UI-ordering fix, requiring no diff to understand.