Bug: iNKA analytic covariance does not input decoupled noise bias #290

In the computation of the iNKA covariance, a fiducial Cell is extracted using cs_util and a noise bias is computed from the catalog. Two branches are possible:

• randoms: Generate multiple Gaussian noise only maps from the catalog and averages the decoupled cells of many realisations. Computes the decouples spectra as is.
• analytical: Uses an analytical description from Nicola et al. (2019) to get the noise bias. The analytical description returns the coupled noise bias. The decoupling is missing in the current implementation.

This bug was caught during the validation of #282 #286 .