Prevent the TapHandler in AvatarTabButton from triggering clicked()

This caused right-clicks on this component (for example, in the space
drawer) to cause clicked() to be called on the delegate.

src/qml/Component/AvatarTabButton.qml

@@ -28,6 +28,8 @@ Delegates.RoundedItemDelegate {
     TapHandler {
         acceptedButtons: Qt.RightButton
         acceptedDevices: PointerDevice.Mouse
+        grabPermissions: PointerHandler.TakeOverForbidden
+        gesturePolicy: TapHandler.WithinBounds
         onTapped: root.contextMenuRequested()
     }