Enable third party test

Author: antonwolfy

tests/third_party/cupy/math_tests/test_floating.py

@@ -29,7 +29,6 @@ def test_copysign_float(self, xp, dtype):
         b = xp.array([-xp.inf, -3, -0.0, 0, 3, xp.inf], dtype=dtype)[None, :]
         return xp.copysign(a, b)
 
-    @pytest.mark.skip("ldexp() is not implemented yet")
     @testing.for_float_dtypes(name="ftype")
     @testing.for_dtypes(["i", "l"], name="itype")
     @testing.numpy_cupy_array_equal()