contrib-slider: look at upgrading to rangeslider v2.3.0

... seeing as [v2.3.0](https://github.com/andreruffert/rangeslider.js/releases/tag/v2.3.0) has a fix for the [bug where dragging the slider also selects surrounding text in IE, Edge and Firefox](https://github.com/andreruffert/rangeslider.js/issues/192)