The proxy filters repodata.json and current_repodata.json, but
repodata.json.bz2 went through the metadata cache unfiltered, and
repodata.json.zst and repodata.jlap reached the download handler and were
passed through. conda tries repodata.json.zst first, so with cooldown on it
got versions still in cooldown.
With cooldown on these now answer 404, and conda falls back to
repodata.json. repodata_from_packages.json is filtered like repodata.json.
