APFitter using deprecated optimization module

[jdtsmith]

Note from astropy.modeling:

Note that the :class:~astropy.modeling.fitting.LevMarLSQFitter fitter, which uses the Levenberg-Marquardt algorithm via the scipy legacy function scipy.optimize.leastsq, is no longer recommended. This fitter supports parameter bounds via an unsophisticated min/max condition whereby during each step of the fitting, parameters that are out of bounds are simply reset to the min or max of the bounds. This can cause parameters to "stick" to one of the bounds if during the fitting process the parameter gets close to the bound. If the models you are fitting make use of bounds, you should make use of one of the other fitters...