fix(ui): style Don't allow button as outline in feedback modal

The "Don't allow" button in the feedback sharing preference modal
should be visually distinct from "Always allow" by using an outline
variant instead of the default solid primary style.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/OutputFeedbackButtons.tsx

@@ -216,6 +216,7 @@ export function OutputFeedbackButtons({
           <DialogFooter>
             <Button
               type="button"
+              variant="outline"
               disabled={!pendingVote || isSaving}
               onClick={() => {
                 if (!pendingVote) return;