astronomy: drop python3-ATpy

ATpy was retired:
https://src.fedoraproject.org/rpms/ATpy/c/cb5d588
the commit notes that astropy is the replacement; it's already
included, so that's fine.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

fedora-live-astronomy_kde.ks

@@ -83,7 +83,6 @@ python3-astroML
 python3-astroquery
 python3-astroscrappy
 python3-APLpy
-python3-ATpy
 python3-ccdproc
 python3-fitsio
 python3-gatspy