sdk-cross-compilation: Only rely on pre-installed packages

We want to ensure that things work out-of-the-box and having the test install
packages would mask issue due to missing packages in the default installation.

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

test-cases/sdk-cross-compilation.yaml

@@ -16,8 +16,6 @@ metadata:
     - "The output should show PASSED."
 
 install:
-  deps:
-    - systemd-container
   git-repos:
     - url: https://gitlab.apertis.org/tests/sdk.git
       branch: 'apertis/v2020dev0'