We rescue from `SignatureTimeInvalidError` but we define it as `InvalidSignatureTimeError`

See discussion here: https://gitlab.slack.com/conversation/C32LCGC1H/p1524775031000032.

We may be trying to rescue from an error that is not initialized as we written it wrongly in authenticate_by_gitlab_geo_node_token!.

Here is a stacktrace from it:

NameError (uninitialized constant Gitlab::Geo::SignatureTimeInvalidError):
  /opt/gitlab/embedded/service/gitlab-rails/ee/lib/api/geo.rb:51:in `rescue in authenticate_by_gitlab_geo_node_token!'