util/http: Change pinned root CA to GeoTrust.
util/http: Change pinned root CA to GeoTrust.

The robot's main CA has switched again (see commit d7edda3), which makes
this library pretty much unusable. We obviously need to find a way to
use the system's CA file in the long term so that things like this won't
happen.

Signed-off-by: aszlig <ee1aa092358634f9c53f01b5a783726c9e21b35a@redmoonstudios.org>

RedMoonStudios/hetzner