servant/config: remove unused language pragmas

servant-server/src/Servant/Server/Internal/Config.hs

@@ -1,20 +1,12 @@
 {-# LANGUAGE CPP                        #-}
 {-# LANGUAGE DataKinds                  #-}
-{-# LANGUAGE DeriveFoldable             #-}
-{-# LANGUAGE DeriveFunctor              #-}
-{-# LANGUAGE DeriveGeneric              #-}
-{-# LANGUAGE DeriveTraversable          #-}
 {-# LANGUAGE FlexibleContexts           #-}
 {-# LANGUAGE FlexibleInstances          #-}
-{-# LANGUAGE FunctionalDependencies     #-}
 {-# LANGUAGE GADTs                      #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE KindSignatures             #-}
 {-# LANGUAGE MultiParamTypeClasses      #-}
-{-# LANGUAGE PolyKinds                  #-}
 {-# LANGUAGE ScopedTypeVariables        #-}
 {-# LANGUAGE TypeOperators              #-}
-{-# LANGUAGE UndecidableInstances       #-}
 
 #include "overlapping-compat.h"