cpu_map: Drop vmx-invvpid-single-context from CPU models

cpu_map: Drop vmx-invvpid-single-context from CPU models

QEMU calls the same feature differently, but translating the names in
libvirt does not make sense because the name in QEMU conflicts with
another feature. QEMU will not change the name for compatibility reasons
so we can just drop our invented name as it is not supported by QEMU.
Apart from this slightly different reason behind the feature being
unsupported by QEMU the situation is similar to vmx-ept-{uc,wb} dropped
in the previous patch and so is the implications.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>