Don't include `beeblink_dfs_tests` in distribution zip

[tom-seddon]

Might end up fixed automatically one switched to GitHub Actions?

[tom-seddon]

Nope... looks like all of volumes is added! beeblink_tubehost_tests is there too, but it's slightly harder to make it show up.

Should have the CI process add only volumes/beeblink? Will that do it?