New version of game will detected when you open the game, then the new version of game will downloaded, after that download complete when you 'refresh' the browser it will open the new version of game.
You can check your new version of game with browser plugin, it will give you event when detected a new version of game
You can check this
construct.net/en/tutorials/offline-games-construct-8
Or if you want your game not caching on server, you can change server configuration OR always delete sw.js and offline.js when publishing to server.