Updated print for dict in `mul`

Here are some results:
In [3]: x = Symbol('x')

In [4]: (3+I/2)**(Integer(1)/2)*x
Out[4]: x*(3 + 1/2*I)^(1/2)

In [5]: (3+Integer(1)/2)**(Integer(1)/2)*x
Out[5]: x*(7/2)^(1/2)