Fix "ttl" typos

Change-Id: I20b99ab09e8c8fb5246e4697b6b32eef54623425
diff --git a/designate_tempest_plugin/config.py b/designate_tempest_plugin/config.py
index 2144eb1..9b86945 100644
--- a/designate_tempest_plugin/config.py
+++ b/designate_tempest_plugin/config.py
@@ -42,7 +42,7 @@
                help="Timeout in seconds to wait for an resource to build."),
     cfg.IntOpt('min_ttl',
                default=0,
-               help="The minimum value to respect when generating ttls"),
+               help="The minimum value to respect when generating ttl"),
     cfg.ListOpt('nameservers',
                 default=[],
                 help="The nameservers to check for change going live"),