Marquardt–Levenberg method issue

[ChabaneAmaury]

While running some tests on the eit_static_jac example, I came accross an issue. It seems this method is broken, as the gtol is going crazy and the results are clearly wrong.
You can recreate it simply by putting the method flag on 'lm' for the eit.gn function.

[liubenyuan]

Yes, I forgot putting method="lm" in eit.gn.

lm seems like instable compared to the kotre regularization. I will dig into issue.