Typo "authtenticated" instead of "authenticated"

Misspelling of "authenticated" found in docstring of
method get_client in client.py

Change-Id: I0b661a6b6008b416341ccbc691739094420723b1

ceilometerclient/client.py

@@ -222,7 +222,7 @@ def Client(version, *args, **kwargs):
 
 
 def get_client(version, **kwargs):
-    """Get an authtenticated client, based on the credentials
+    """Get an authenticated client, based on the credentials
         in the keyword args.
 
     :param api_version: the API version to use ('1' or '2')