Add documentation note for deletion

[rajivsarvepalli]

Added documentation note saying keywords can be added to delete with no impact. Some note like:

You can use keywords with delete like so:

n_d = s.query(Data).filter(Data.data_p1 >= 13).delete(synchronize_session=False)

and this will work. However, the keyword arguments have no impact on the delete command, but merely are allowed so as little code as possible has to be changed. However, delete cannot be used with objects such as:

a = Data(pk1=11, data_p1=31.5, data_p2=67.1, name="test13")
n_d = s.delete(a)

The above code is invalid when using UnifiedAlchemyMagicMock as the session object s.