Remove orphan instance

Author: jasagredo

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/LedgerDB/V2.hs

@@ -14,7 +14,6 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-{-# OPTIONS_GHC -Wno-orphans #-}
 
 module Ouroboros.Consensus.Storage.LedgerDB.V2 (mkInitDb) where
 
@@ -455,10 +454,6 @@ deriving instance
   ) =>
   NoThunks (LedgerDBEnv m l blk)
 
-instance NoThunks (LSM.Session m) where
-  showTypeOf _ = "Session"
-  wNoThunks _ _ = pure Nothing
-
 {-------------------------------------------------------------------------------
   The LedgerDBHandle
 -------------------------------------------------------------------------------}