add UndecidableInstances for ghc8.10

src/Simplex/Chat/Messages.hs

@@ -12,6 +12,7 @@
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -fno-warn-ambiguous-fields #-}
 
 module Simplex.Chat.Messages where