Mirrors listed in mirrors.json are non-functional

[chreekat]

There are two mirrors listed.

1. "http://hackage.fpcomplete.com/". This one went offline last week. It had been deprecated for a while already.
2. "http://objects-us-east-1.dream.io/hackage-mirror/". This is a deprecated URL scheme for dream.io buckets. I'm not sure when it stopped working, but as of today it serves ad-laden 404s.

Replacements:

1. "https://hackage-mirror.haskell.foundation/". This is one I (acting for the Haskell Foundation) set up when I adopted the Stackage infrastructure from FP Complete.
2. "https://s3.us-east-005.dream.io/hackage-mirror/". According to davean, this is the new URL scheme for dream.io.