Remove obsolete HORIZONS automation from Makefile
Remove obsolete HORIZONS automation from Makefile

skyfielders/python-skyfield,ozialien/python-skyfield,ozialien/python-skyfield,GuidoBR/python-skyfield,GuidoBR/python-skyfield,skyfielders/python-skyfield,exoanalytic/python-skyfield,exoanalytic/python-skyfield