Remove redundant pattern matches

In ghc/ghc!963, pattern match
checking got more precise in the presence of COMPLETE pragmas. That
uncovered that there are redundant pattern matches in `binary`.

src/Data/Binary/Class.hs

@@ -974,7 +974,6 @@ putTypeRep (Fun arg res) = do
     put (3 :: Word8)
     putTypeRep arg
     putTypeRep res
-putTypeRep _ = error "GHCi.TH.Binary.putTypeRep: Impossible"
 
 getSomeTypeRep :: Get SomeTypeRep
 getSomeTypeRep = do