[ci] Don't install manila-tempest-plugin system-wide

System-wide installation via the tempest plugin's
devstack-plugin is unnecessary since we set the
"TEMPEST_PLUGINS" devstack localrc variable with
manila-tempest-plugin, and that should handle installing
the plugin alongside other tempest requirements within
a test virtual environment.

Change-Id: Id312005dc0cc9e039a9c6a8a58476965e8d6954d
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>
diff --git a/zuul.d/manila-tempest-jobs.yaml b/zuul.d/manila-tempest-jobs.yaml
index 7d7b08e..164db72 100644
--- a/zuul.d/manila-tempest-jobs.yaml
+++ b/zuul.d/manila-tempest-jobs.yaml
@@ -28,7 +28,6 @@
         - manila-tempest-plugin
       devstack_plugins:
         manila: https://opendev.org/openstack/manila
-        manila-tempest-plugin: https://opendev.org/openstack/manila-tempest-plugin
       devstack_services:
         cinder: false
         s-account: false
@@ -88,7 +87,6 @@
         - manila-tempest-plugin
       devstack_plugins:
         manila: https://opendev.org/openstack/manila
-        manila-tempest-plugin: https://opendev.org/openstack/manila-tempest-plugin
       test_results_stage_name: test_results
       zuul_copy_output:
         '{{ devstack_base_dir }}/tempest/etc/tempest.conf': logs