Correct top comment in Query/Server

I assumed this was a copy-paste+forgetting to change the header comment.

Signed-off-by: Agata Murawska <agatamurawska@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

htools/Ganeti/Query/Server.hs

 {-# LANGUAGE BangPatterns #-}
 
-{-| Implementation of the Ganeti confd types.
+{-| Implementation of the Ganeti Query2 server.
 
 -}