This is a diff file. It should be applied by the patch utility, which is included to any Linux. If you don’t have the patch utility (Windows user for example), you could replace the file wp-content/plugins/openid/f/openid.js with this one: https://slavach.info/wp-content/plugins/openid/f/openid.js
I’m not sure that your problem is the same, as far as the openid checkbox is present at your page. In my case, this field hadn’t been visible, until I edited the openid.js.