Remove nova-lxd plugin from blacklist

This commit removes the nova-lxd plugin from the blacklist. The proposed
patch was already merged, so this plugin should pass the sanity job now.

Change-Id: I72eb62af993bc978127185a1aed0763af18ce9f3
diff --git a/tools/generate-tempest-plugins-list.py b/tools/generate-tempest-plugins-list.py
index f07410f..4582764 100644
--- a/tools/generate-tempest-plugins-list.py
+++ b/tools/generate-tempest-plugins-list.py
@@ -57,7 +57,6 @@
     'openstack/neutron-dynamic-routing',
     # https://review.opendev.org/#/c/637718/
     'openstack/neutron-vpnaas',  # https://review.opendev.org/#/c/637719/
-    'x/nova-lxd',  # https://review.opendev.org/#/c/638334/
     'x/valet',  # https://review.opendev.org/#/c/638339/
 ]