Fixed calculation error on lesson 2 notebook

I think this is correct...?

    In [11]: matrix1
    Out[11]: [[1, 3, 9, 2], [2, 4, 6, 8]]

    In [12]: matrix2
    Out[12]: [[2, 1], [3, 2], [6, 0], [5, 4]]

    In [13]: np.dot(matrix1,matrix2)
    Out[13]:
    array([[75, 15],
           [92, 42]])