Replace lsb-core package that is unavailable in later versions of Ubuntu

What does this merge request do and why?

As discussed in: gitlab!188011 (comment 2795603962), and reported by @SharkyBytes, having lsb-core as a required package for GDK for Ubuntu installations might cause installation problems.

It appears that that package is not available for later versions of Ubuntu: https://packages.ubuntu.com/search?keywords=lsb-core.

Let's replace the package with lsb-release so that the Ubuntu package list and Debian package list are identical.

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This MR references an issue describing the change.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.