fix: add apt-get update before installing Linux packages

The ubuntu-latest ADO agent image has a stale package index,
causing libgtk-4-* packages to 404 from security.ubuntu.com.
Running apt-get update first ensures the index is fresh.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: hl662

.pipelines/integration-test.yaml

@@ -87,6 +87,7 @@ jobs:
         displayName: Build packages
 
       - script: |
+          sudo apt-get update
           sudo apt-get install -y libsecret-1-dev
           sudo apt-get install -y dbus-x11
           sudo apt-get install -y gnome-keyring