docs: remove Gitter link since it is no longer maintained (#911)

Author: trollepierre

Diff for: README.md

@@ -35,7 +35,7 @@ Refer to the [documentation](https://vue-test-utils.vuejs.org/)
 
 ## Questions
 
-For questions and support please use the [Discord chat room](https://vue-land.js.org/), [Gitter chat room](https://gitter.im/vuejs/vue), or [the official forum](http://forum.vuejs.org). The issue list of this repo is **exclusively** for bug reports and feature requests.
+For questions and support please use the [Discord chat room](https://vue-land.js.org/) or [the official forum](http://forum.vuejs.org). The issue list of this repo is **exclusively** for bug reports and feature requests.
 
 ## Issues