Treat these answers as version-specific. For example, we don't want to edit answers for 13.04 release to add information for 18.04 release ( unless it's absolutely necessary and relevant ). Same approach applies here: if the answer relied on Software Center specifically, editing the links out of the answer affects the original intent of the poster. As much as we like to keep everything current, some answers have to remain as they are for historical value and context. They may still be useful and the software might be installed from other means (apt,snaps,github, etc), so full answer removal is undesirable. Questions also may be specific to the time when they were posted.
Better approach would be to post a comment under the answer (or better yet under the question in bold text) to draw attention that the links won't work. If you know alternative method of installing the desired software - edit the answer to add that information.