Modify the list syntax error

The "key pair" and "security group" are the sub title for the
"Access and security" list, this patch fix them.

Change-Id: I4d0b13eb5220ab45a44c09913d82dd636978d68d

doc/user-guide/source/cli_launch_instances.rst

@@ -28,17 +28,17 @@ Before you can launch an instance, gather the following parameters:
 - Access and security credentials, which include one or both of the
   following credentials:
 
-- A **key pair** for your instance, which are SSH credentials that
-  are injected into images when they are launched. For the key pair
-  to be successfully injected, the image must contain the
-  ``cloud-init`` package. Create at least one key pair for each
-  project. If you already have generated a key pair with an external
-  tool, you can import it into OpenStack. You can use the key pair
-  for multiple instances that belong to that project.
+  - A **key pair** for your instance, which are SSH credentials that
+    are injected into images when they are launched. For the key pair
+    to be successfully injected, the image must contain the
+    ``cloud-init`` package. Create at least one key pair for each
+    project. If you already have generated a key pair with an external
+    tool, you can import it into OpenStack. You can use the key pair
+    for multiple instances that belong to that project.
 
-- A **security group** that defines which incoming network traffic
-  is forwarded to instances. Security groups hold a set of firewall
-  policies, known as *security group rules*.
+  - A **security group** that defines which incoming network traffic
+    is forwarded to instances. Security groups hold a set of firewall
+    policies, known as *security group rules*.
 
 - If needed, you can assign a **floating (public) IP address** to a
   running instance.