Remove cleanup of [pci] passthrough_whitelist

This logic was added during the previous cycle[1] as part of migration
to the new [pci] device_spec parameter. The old parameter should be
removed when a deployment is upgraded to Zed so we no longer need this
beyond Zed.

[1] 502aec2406

Change-Id: I1e89883a9044b4d6bfd810d0a616b6a29aeff050

manifests/compute/pci.pp

@@ -26,9 +26,4 @@ class nova::compute::pci(
   nova_config {
     'pci/device_spec': value => $passthrough_real;
   }
-
-  # TODO(tkajinam): Remove this after Zed release.
-  nova_config {
-    'pci/passthrough_whitelist': ensure => absent;
-  }
 }