Don't show Refresh action on mobile

On Mobile, the common and expected behavior is pulling down the view to
refrehs it, so we don't need to show an explicit button.

discover/qml/DiscoverWindow.qml

@@ -100,6 +100,10 @@ Kirigami.ApplicationWindow
         icon.name: "view-refresh"
         onTriggered: action.trigger()
         enabled: action.enabled
+        // Don't need to show this action in mobile view since you can pull down
+        // on the view to refresh, and this is the common and expected behavior
+        //on that platform
+        visible: window.wideScreen
         tooltip: shortcut
 
         shortcut: "Ctrl+R"