tests: Remove redundant aarch64 tests

My commit 7b9de914 added some aarch64 CPU test cases. I wanted to test
two different code paths but inadvertently added two of the same test
cases.

The second code path (using <cpu><model>host</model</cpu>) isn't easily
exercised via the qemu tests anyways, I'll need to look elsewhere.

Regardless, remove the redundant tests for now

tests/qemuxml2xmloutdata/qemuxml2argv-aarch64-cpu-passthrough.xml

@@ -1,27 +0,0 @@
-<domain type="kvm">
-  <name>aarch64test</name>
-  <uuid>496d7ea8-9739-544b-4ebd-ef08be936e8b</uuid>
-  <memory>1048576</memory>
-  <currentMemory>1048576</currentMemory>
-  <vcpu placement='static'>1</vcpu>
-  <os>
-    <type arch="aarch64" machine="virt">hvm</type>
-  </os>
-  <features>
-    <acpi/>
-    <apic/>
-    <pae/>
-  </features>
-  <cpu mode='host-passthrough'/>
-  <clock offset="utc"/>
-  <on_poweroff>destroy</on_poweroff>
-  <on_reboot>restart</on_reboot>
-  <on_crash>restart</on_crash>
-  <devices>
-    <emulator>/usr/bin/qemu-system-aarch64</emulator>
-    <disk type='file' device='disk'>
-      <source file='/aarch64.raw'/>
-      <target dev='vda' bus='virtio'/>
-    </disk>
-  </devices>
-</domain>