Explore tolerance choice in gas_compact_multiphysics tutorial

[aprilnovak]

As reported by Yifeng Che of INL, it seems we may have too loose a convergence tolerance for the steady state detection in the gas compact multiphysics tutorial. When she tightened this tolerance, she saw noticeable differences in the converged temperatures. We should tighten this tolerance, or else document why it is rather loose for the tutorial (so that users can run the input files faster).