Speed up MPS simulator test (#4063)
Speed up MPS simulator test (#4063)

This was create 288 circuits and running 4 simulations per circuit.  The test took >9 seconds.  I've replaced this with random circuits and reduced the number to of circuits to 5 to get this to around 2 seconds.

I don't think this test was testing anything special about the two qubit circuit, but if so then this won't be a good fix so you should yell.   
quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq