Fix outdated client message when up to date

[HebaruSan]

Problem

The new "Repositories updated, but found modules that require a new version of CKAN. Checking for updates..." message appears on every update, regardless of whether your client is outdated.

Cause

In #4026 we treated an ArchiveEntry tuple as indicating an unsupported spec version if its first item was null, but this is also expected for download_counts.json, builds.json, and repositories.json. The correct indicator is when all of the first four items are null.

Changes

Now we check whether all of the first four items in the tuple are null.