Revert "Add Data instance for Const"

This reverts commit 07e40e90.

This was meant for a local branch, but accidentally wound up in master. Oops.

libraries/base/Data/Data.hs

@@ -9,7 +9,6 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE TypeInType #-}
 {-# LANGUAGE TypeOperators #-}
 
 -----------------------------------------------------------------------------
@@ -1198,9 +1197,6 @@ deriving instance (Coercible a b, Data a, Data b) => Data (Coercion a b)
 -- | @since 4.9.0.0
 deriving instance Data a => Data (Identity a)
 
--- | @since 4.10.0.0
-deriving instance (Typeable k, Data a, Typeable (b :: k)) => Data (Const a b)
-
 -- | @since 4.7.0.0
 deriving instance Data Version
 

libraries/base/changelog.md

@@ -26,8 +26,6 @@
   * Add `Semigroup` instance for `IO`, as well as for `Event` and `Lifetime`
     from `GHC.Event` (#12464)
 
-  * Add `Data` instance for `Const` (#12438)
-
 ## 4.9.0.0  *May 2016*
 
   * Bundled with GHC 8.0