Unified GameMaker releases feed missing content after 10/13

[adam-coster]

It looks like GameMaker has changed something about the content of their RSS feeds, since the latest few releases in the Unified feed are missing the lists of changes in those versions.

[adam-coster]

Turns out this is due to beta feeds no longer containing any info, and instead pointing to GitHub issues. @BscotchSeth We should revisit this in a few months to see if they've settled on something we can automatically consume in the unified release notes, but otherwise I think we're just stuck with this suboptimal situation!