removed unnecessary language extension

src/UI/Callbacks.hs

@@ -1,5 +1,3 @@
-{-# LANGUAGE ExistentialQuantification #-}
-
 module UI.Callbacks where
 
 

src/UI/UIBaseData.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
+-- data and classes are separated into several modules to avoid cyclic dependencies with the Type module
 
 module UI.UIBaseData where