ben is marked for autoremoval from testing

[Debian testing autoremoval watch]

ben 0.9.0 is marked for autoremoval from testing on 2020-04-04

It (build-)depends on packages with these RC bugs:
911166: gtksourceview2: Do not release with Bullseye
951707: gringo: gringo ftbfs with Python 3.8
951842: gringo: gringo needs a new upstream, and fixes for python3.8