Fix Applicable/Replace instance according to semantics (2)

src/Data/Patch/Class.hs

@@ -226,9 +226,14 @@ instance (Show a, Eq a) => Action (Replace a) a where
           ]
 -}
 
+{- semantics (1)
 instance Eq a => Applicable (Replace a) a where
   applicable Keep          _ = mempty
   applicable (Replace o _) a = check (o == a) "Applying a value different than the *old* value of a Replace patch"
+-}
+
+instance Applicable (Replace a) a where
+  applicable _ _ = mempty
 
 type instance Patched (Replace a) = a