updated iota to theta_jn in tutorials
Updates the parameter representing angle between angular momentum and line of sight from 'iota' to 'theta_jn'. This brings the tutorial's parameter naming conventions up to date with the rest of the code.
Updates the parameter representing angle between angular momentum and line of sight from 'iota' to 'theta_jn'. This brings the tutorial's parameter naming conventions up to date with the rest of the code.