Try giving aarch64 VMs more RAM to see if it helps
    
    desktop tests are very very fail-y on aarch64, with all kinds of
    random failure cases. I suspect the worker hosts are just *slow*,
    but they do have plenty of RAM per worker instance, so let's try
    throwing a bit more RAM at each one and see if that helps at all.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>