Use the networking-l2gw project new location

networking-l2gw and networking-l2gw-tempest-plugin are
imported to new location now and supposed to be retired from
openstack/namespace[1].

-https://review.opendev.org/#/c/744110/

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-June/015647.html

Change-Id: If00bffe2b6d303686e15060f6b03400ad5a3089f
diff --git a/tools/generate-tempest-plugins-list.py b/tools/generate-tempest-plugins-list.py
index 5ffef3e..fba44a5 100644
--- a/tools/generate-tempest-plugins-list.py
+++ b/tools/generate-tempest-plugins-list.py
@@ -41,7 +41,7 @@
     'x/intel-nfv-ci-tests',  # https://review.opendev.org/#/c/634640/
     'openstack/networking-generic-switch',
     # https://review.opendev.org/#/c/634846/
-    'openstack/networking-l2gw-tempest-plugin',
+    'x/networking-l2gw-tempest-plugin',
     # https://review.opendev.org/#/c/635093/
     'openstack/networking-midonet',  # https://review.opendev.org/#/c/635096/
     'x/networking-plumgrid',  # https://review.opendev.org/#/c/635096/