[pkg-cinnamon] Bug#864938: cinnamon-screensaver-webkit-plugin: Drop alt dep on gir1.2-webkit2-3.0

[Jeremy Bicha]

Package: cinnamon-screensaver-webkit-plugin
Version: 3.2.13-4
Severity: important
Tags: buster
User: pkg-webkit-maintainers at lists.alioth.debian.org
Usertags: oldlibs webkit1
Forwarded: https://github.com/linuxmint/cinnamon-screensaver/issues/232

I noticed this in Debian and I reported this to Cinnamon upstream too
which has the same issue.

Please drop the alternate dependency on gir1.2-webkit2-3.0 since it is
part of the unmaintained webkitgtk source package. The newer
gir1.2-webkit2-4.0 is available in Debian 8 and newer releases.

Thanks,
Jeremy Bicha