Updated from generate-devstack-plugins-list

Change-Id: I2ba736a97377ba1823b3d48983ebf6e4640c72aa

Author: OpenStack Proposal Bot

doc/source/plugin-registry.rst

@@ -173,6 +173,7 @@ stackube                               `git://git.openstack.org/openstack/stacku
 storlets                               `git://git.openstack.org/openstack/storlets <https://git.openstack.org/cgit/openstack/storlets>`__
 stx-config                             `git://git.openstack.org/openstack/stx-config <https://git.openstack.org/cgit/openstack/stx-config>`__
 stx-fault                              `git://git.openstack.org/openstack/stx-fault <https://git.openstack.org/cgit/openstack/stx-fault>`__
+stx-update                             `git://git.openstack.org/openstack/stx-update <https://git.openstack.org/cgit/openstack/stx-update>`__
 tacker                                 `git://git.openstack.org/openstack/tacker <https://git.openstack.org/cgit/openstack/tacker>`__
 tap-as-a-service                       `git://git.openstack.org/openstack/tap-as-a-service <https://git.openstack.org/cgit/openstack/tap-as-a-service>`__
 tap-as-a-service-dashboard             `git://git.openstack.org/openstack/tap-as-a-service-dashboard <https://git.openstack.org/cgit/openstack/tap-as-a-service-dashboard>`__