Update or remove cube_skymatch

[stscijgbot-jp]

Issue JP-3899 was created on JIRA by Melanie Clarke:

There is a step defined in the jwst package that does not appear to be used or documented anywhere, called 'cube_skymatch'.  It appears to be intended to match sky backgrounds for 3D IFU cubes with reference to a separate set of 2D models.  It is separate from and does not interact with the other IFU sky matching step (mrs_imatch), called from the calwebb_spec3 pipeline.

The cube_skymatch step is not called in any of the pipelines and is not documented in readthedocs.  From the git history, it looks like the last time it was significantly modified was around 2016-2017.  

Can we remove this module?  Or is there interest in maintaining or updating it?