Telling Kaniko about Heptapod internal tooling CA

(used for Docker images proxy caching)

A better solution might be to fetch it from the Heptapod web site, assuming it would stay
the same in all locations (that was already the intent anyway).

In the Kaniko image, `wget` is available, provided by busybox.
3 jobs for branch/default in 12 minutes and 13 seconds (queued for 1 second)