Remove pformat from stochastic swap log messages (#3812)
Remove pformat from stochastic swap log messages (#3812)

When profiling a level 0 transpile of a 20x50 random circuit the timing
data shows that after switching to retworkx the largest chunk of time in
in stochastic swap's _layer_permutation function is spent calling pformat
for log messages. This is just for debugging and is unecessary, and in a
world where we're no longer bottlenecked on dag operations a signifcant
cost to the run time.
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py