Fix the apertis-tests branch for older releases

Now that everything has been branched for the next release, use the
matching apertis-tests branch for our LAVA tests.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

Jenkinsfile

@@ -24,7 +24,7 @@ ostree_pull_url = image_url_prefix + "/${ostree_path}"
 
 test_repo_url = "git@gitlab.apertis.org:infrastructure/apertis-tests.git"
 test_repo_credentials = 'df7b609b-df30-431d-a942-af263af80571'
-test_repo_branch = 'master'
+test_repo_branch = release
 test_lava_credentials = 'apertis-lava-user'
 
 demopack = "https://images.apertis.org/media/multimedia-demo.tar.gz"