Remove redundant changeLog field

Summary:
BUG: 387041
FIXED-IN: 5.12.0

For Debian packages, PackageKit manufactures the `updateText` and `updates` fields from the package's changelog. PackageKit gives us the `updateText` and `updates` fields, but also includes the original text used to synthesize them in a field called `changeLog`.

So we should only display `updateText` and `updates`, since `changeLog` is just the the raw information used to synthesize them, and if we show it too, there's duplicate information.

For more information about this, see https://github.com/hughsie/PackageKit/issues/227

Test Plan:
**This change needs testing from people who are not using Debian-based distros to make sure it didn't break anything for them!**

I tested in KDE Neon, a Debian-based distro. Before:
{F5644556}

After:
{F5644557}

Other entries still show up and are not affected.

Reviewers: apol, #discover_software_store

Reviewed By: apol, #discover_software_store

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D9850