After removing the host CPU model re-computation,
this function is no longer necessary.

This reverts commits:
commit d0498881
  virQEMUCapsFreeHostCPUModel: Don't always free host cpuData
commit 5276ec71
  testUpdateQEMUCaps: Don't leak host cpuData
Signed-off-by: NJán Tomko <jtomko@redhat.com>