According to Saucelab's documentation, it's easy to fix.

Default to Latest Version of Chrome or Firefox
If you want to use the latest stable version of Google Chrome or Firefox that Sauce supports, you can use "version": "latest". You can also use "version": "latest-1" or "version": "latest-2", etc. to request the next most recent versions of a browser. For example, if the latest stable version of Chrome is 48, you can request "latest-2" to use Chrome 46.

To back up our word on supported browsers, we should put latest-1 for each major browsers.