Release procedure: we don't use milestones anymore (#275)

Author: raboof

RELEASING.md

@@ -3,7 +3,6 @@
 1. Create a [new release](https://github.com/lightbend/genjavadoc/releases/new) with:
   * the next tag version (e.g. `v0.11`)
   * title and release description including notable changes
-  * link to the [milestone](https://github.com/lightbend/genjavadoc/milestones) showing an overview of closed issues for this release
 2. This should push the artifacts from travis to sonatype, and then close and release the repository.
 
 ## Back-releasing for a new Scala version