This is the change to exclude the devise :timedout key from showing up in the flash messages (Issue #1005). I don't have a spec for this because I'm not quite sure how to add one for this functionality but this is my proposed fix.
Note that this is a Rails-specific fix because it relies on ActiveSupport's addition of Hash#except
Exclude devise :timedout from flash messages
There is another layout that is rendered for the logged out views which needs to be updated also https://github.com/gregbell/active_admin/blob/master/app/views/layouts/active_admin_logged_out.html.erb
The logged out views should really be rendered the same way as the logged in ones. For now though, we can just update it in the second spot.