tests: qemuxml2argv: Use existing non-virt machine in 'aarch64-gic-not-virt'

Use 'versatilepb' instead of a fake 'non-virt' machine type.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

tests/qemuxml2argvdata/aarch64-gic-not-virt.xml

@@ -4,7 +4,7 @@
   <memory unit='KiB'>1048576</memory>
   <vcpu placement='static'>1</vcpu>
   <os>
-    <type arch='aarch64' machine='not-virt'>hvm</type>
+    <type arch='aarch64' machine='versatilepb'>hvm</type>
   </os>
   <features>
     <gic/>