Change fraction of interlopers parameter to f_corr

[chiaramoretti]

📝 Issue Summary

It was decided to modulate the amplitude of the spectroscopic observables using the fraction of correct galaxies fcorr instead of the fraction of interlopers fout, we need to change the parameter.

✅ Expected Outcome

• Goal 1: _Pk2d_tot and _Pk2d_term_tot use self.parameters["fout"]**2 instead of (1.0 - self.parameters["fout"]) ** 2

🔄 Steps to Reproduce (if applicable)

1. Test (and implement) the new parameter in the playground notebook