Repository size greater than 1 GB message

Hi there,
we have a repo (click me) that keeps telling us "This repository's size is over 1 GB. Read more on how to reduce the size of your repository."

git count-objects -v -H
responds with:

count: 0
size: 0 bytes
in-pack: 25
packs: 1
size-pack: 107.64 KiB
prune-packable: 0
garbage: 0
size-garbage: 0 bytes

I assume that's the same "issue" that was present in those issues:
Issue 1
Issue 2
and is related to the garbage collection. Would be nice if someone could force garbage collection on the repo.

Thanks in advance!
EB