docs: update FAQ about :async feature

Author: darwin

docs/faq.md

@@ -54,7 +54,7 @@ Technical details are described in [the source file][11].
 
 ### What is the `:async` feature?
 
-This is an experimental feature.
+This is an experimental feature. Please note that this feature is [no longer needed](https://github.com/binaryage/cljs-devtools/issues/20) in Chrome 65.0.3321 and newer.
 
 Chrome DevTools support [async call stacks][1]. It would be great to see full chains of async stack traces for code generated by
  ClojureScript compiler, especially when using [core.async][2] library. To give you concrete picture, we want to see [this][3] instead of [this][4].