Bug#885677: liblablgtksourceview2-ocaml: Depends on unmaintained gtksourceview2

[Jeremy Bicha <jbicha@debian.org>]

Control: reopen -1

You can't drop liblablgtksourceview2-ocaml-dev as long as stuff still
depends and build-depends on it.

coq
lablgtk-extra
laby
marionnet

gtksourceview2 will be included in Debian 10 "Buster" but we will try
to remove it early in the Bullseye series. [1]

Therefore, I suggest bringing that package back, then you can lower
the severity of this bug to Important. We'll have to figure something
out for Bullseye.

[1] https://lists.debian.org/debian-devel/2018/11/msg00570.html

Thanks,
Jeremy Bicha