Stop disabling unload from JS

This should be rather controlled from the browser profile settings.
Also this was not only prevent the Installer window from closing,
but was giving annoying popups when links were about to be opened.

src/components/app.jsx

@@ -56,9 +56,6 @@ export const Application = () => {
             return;
         }
 
-        // Before unload ask the user for verification
-        window.onbeforeunload = () => "";
-
         dispatch(setCriticalErrorAction());
 
         Promise.all(clients.map(Client => new Client(address, dispatch).init()))