[zenity] CI: Add apt-get update line to build_ubuntu

[Logan Rathbone <larathbone src gnome org>]

commit ec4380a4bc6f7d34d138c689a8bd3b36b6ec11e2
Author: Logan Rathbone <poprocks gmail com>
Date:   Sat Jul 2 13:10:45 2022 -0400

    CI: Add apt-get update line to build_ubuntu

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 1c61c196..369b8090 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -21,6 +21,7 @@ build_fedora:
 build_ubuntu:
   image: ubuntu:rolling
   before_script:
+    - apt-get update
     - apt-get install -q -y --no-install-recommends $UBUNTU_DEPENDENCIES
   script:
     - meson --buildtype=debug -Dlibnotify=true -Dwebkitgtk=true build