Change testing repository to Artifactory (#1027)

Signed-off-by: Ben Clark <ben@benjyc.uk>

installation/linux.md

@@ -92,7 +92,7 @@ Then, you can choose between, *Official (Stable)*, *Beta* or *Snapshot* builds:
     Add the **openHAB 2 Beta Repository** to your systems apt sources list:
 
     ```shell
-    echo 'deb https://dl.bintray.com/openhab/apt-repo2 testing main' | sudo tee /etc/apt/sources.list.d/openhab2.list
+    echo 'deb https://openhab.jfrog.io/openhab/openhab-linuxpkg testing main' | sudo tee /etc/apt/sources.list.d/openhab2.list
     ```
 
 -   **Snapshot Release**