Corrected minor error (forgot to delete old instance).

cabal-install/tests/UnitTests/Distribution/Client/ProjectConfig.hs

@@ -564,16 +564,6 @@ instance Arbitrary RemoteRepo where
           shortListOf1 5 (oneof [ choose ('0', '9')
                                 , choose ('a', 'f') ])
 
-instance Arbitrary UserConstraint where
-    arbitrary =
-      oneof
-        [ UserConstraintVersion   <$> arbitrary <*> arbitrary
-        , UserConstraintInstalled <$> arbitrary
-        , UserConstraintSource    <$> arbitrary
-        , UserConstraintFlags     <$> arbitrary <*> shortListOf1 3 arbitrary
-        , UserConstraintStanzas   <$> arbitrary <*> ((\x->[x]) <$> arbitrary)
-        ]
-
 instance Arbitrary UserConstraint where
     arbitrary =
       oneof [ UserConstraint UserUnqualified <$> arbitrary <*> prop