agl-compositor: Drop gnome-menus

Since now maynard ships its own menu file, installing gnome-menus is not
longer needed, so drop it to avoid installing python and all its
dependencies.

Signed-off-by: Walter Lozano <walter.lozano@collabora.com>

test-cases/agl-compositor.yaml

@@ -37,8 +37,6 @@ run:
     - "Verify that a list of applications is shown"
     - "Enable Development repositories"
     - $ sudo apertis-dev
-    - "Install gnome-menus"
-    - $ sudo apt install gnome-menus
     - "Install pavucontrol"
     - $ sudo apt install pavucontrol
     - "Click on launcher button in the top left to display the installed apps"