UserGuide: Update broken link

This link breaks on the offline version.

docs/UserGuide.adoc

@@ -10,6 +10,7 @@ ifdef::env-github[]
 :tip-caption: :bulb:
 :note-caption: :information_source:
 endif::[]
+:repoURL: https://github.com/se-edu/addressbook-level4
 
 By: `Team SE-EDU`      Since: `Jun 2016`      Licence: `MIT`
 
@@ -21,7 +22,7 @@ By: `Team SE-EDU`      Since: `Jun 2016`      Licence: `MIT`
 Having any Java 8 version is not enough. +
 This app will not work with earlier versions of Java 8.
 +
-.  Download the latest `addressbook.jar` from the link:../../../releases[releases] tab.
+.  Download the latest `addressbook.jar` link:{repoURL}/releases[here].
 .  Copy the file to the folder you want to use as the home folder for your Address Book.
 .  Double-click the file to start the app. The GUI should appear in a few seconds.
 +