Fix doc formating issue

Change-Id: I9aa8c1fd114e4f4329e06ac263f337ea566d8355
diff --git a/doc/source/plugins.rst b/doc/source/plugins.rst
index 70469d6..31987bc 100644
--- a/doc/source/plugins.rst
+++ b/doc/source/plugins.rst
@@ -99,7 +99,7 @@
       should exist at this point.
    -  **extra** - Called near the end after layer 1 and 2 services have
       been started.
-   - **test-config** Called at the end of devstack used to configure tempest
+   - **test-config** - Called at the end of devstack used to configure tempest
       or any other test environments
 
 -  **unstack** - Called by ``unstack.sh`` before other services are shut