revert no-longer-necessary

Author: jbrockmendel

pandas/tests/arithmetic/test_timedelta64.py

@@ -497,7 +497,6 @@ def test_addition_ops(self):
             tdi + Index([1, 2, 3], dtype=np.int64)
 
         # this is a union!
-        # FIXME: don't leave commented-out
         # pytest.raises(TypeError, lambda : Index([1,2,3]) + tdi)
 
         result = tdi + dti  # name will be reset