Revert some docs changes from multi-delete

The headers in the doc files are the commands, not a description.

I missed thiese in the original reviews:
https://review.openstack.org/140567
https://review.openstack.org/140581

Change-Id: Iae2631f6b485e8c568ff305e5992c193f80ebe71

Author: Dean Troyer

doc/source/command-objects/project.rst

@@ -47,12 +47,12 @@ Create new project
 
     New project name
 
-project(s) delete
------------------
+project delete
+--------------
 
 Delete project(s)
 
-.. program:: project(s) delete
+.. program:: project delete
 .. code:: bash
 
     os project delete

doc/source/command-objects/role.rst

@@ -56,12 +56,12 @@ Create new role
 
     New role name
 
-role(s) delete
---------------
+role delete
+-----------
 
 Delete role(s)
 
-.. program:: role(s) delete
+.. program:: role delete
 .. code:: bash
 
     os role delete

doc/source/command-objects/server.rst

@@ -117,18 +117,18 @@ Create a new server
 :option:`<server-name>`
     New server name
 
-server(s) delete
-----------------
+server delete
+-------------
 
-Delete server(s) command
+Delete server(s)
 
 .. code:: bash
 
     os server delete
         <server> [<server> ...]
 
 :option:`<server>`
-    Server (name or ID)
+    Server to delete (name or ID)
 
 server list
 -----------

doc/source/command-objects/user.rst

@@ -69,12 +69,12 @@ Create new user
 
     New user name
 
-user(s) delete
---------------
+user delete
+-----------
 
 Delete user(s)
 
-.. program:: user(s) delete
+.. program:: user delete
 .. code:: bash
 
     os user delete