Remove the useless nova_ssh configure in the passwords.yml

The nova_ssh_private_key and nova_ssh_public_key is useless, and
they should not be merged.

Change-Id: I7e7178398242060a78fe7caee6e14fa77f2ffe35
Closes-Bug: #1576199

etc/kolla/passwords.yml

@@ -65,9 +65,6 @@ manila_keystone_password:
 
 memcache_secret_key:
 
-nova_ssh_private_key:
-nova_ssh_public_key:
-
 nova_ssh_key:
   private_key:
   public_key: