[chore] Update guide. So long Bintray [ci skip]

Author: aalmiray

docs/guide/src/docs/asciidoc/introduction.adoc

@@ -6,9 +6,7 @@ Ikonli provides icon packs that can be used in Java applications. Currently Swin
 
 == Download
 
-Ikonli and all of its icon packs can be downloaded from Bintray
-image:https://api.bintray.com/packages/{project-owner}/{project-repo}/ikonli/images/download.svg[link="https://bintray.com/{project-owner}/{project-repo}/ikonli/_latestVersion"]
-and Maven Central
+Ikonli and all of its icon packs can be downloaded from Maven Central
 image:https://img.shields.io/maven-central/v/{project-group}/ikonli-core.svg?label=maven[link="https://search.maven.org/#search|ga|1|{project-group}"].
 
 You must select a binary that matches your target UI toolkit, such as