remove orphan instance to fix test

Author: kokobd

lsp/test/JsonSpec.hs

@@ -159,14 +159,6 @@ smallList = resize 3 . listOf
 instance (Arbitrary a) => Arbitrary (List a) where
   arbitrary = List <$> arbitrary
 
-instance Arbitrary J.Value where
-  arbitrary = oneof
-    [ J.String <$> arbitrary
-    , J.Number <$> arbitrary
-    , J.Bool <$> arbitrary
-    , pure J.Null
-    ]
-
 -- ---------------------------------------------------------------------
 
 instance Arbitrary DidChangeWatchedFilesRegistrationOptions where