Fix compatibility with Grafana v9.1.3 snapshot API
Fixes our tooling for testing dashboard changes.
Instead of this:
$ ./test-dashboard.sh gitaly/host-detail.dashboard.jsonnet
API call to https://dashboards.gitlab.net/api/snapshots failed with 400:
"Creating a local snapshot requires a dashboard"
We will go back to getting this:
$ ./test-dashboard.sh gitaly/host-detail.dashboard.jsonnet
Installed https://dashboards.gitlab.net/dashboard/snapshot/HkBPmPLwc475asfuGCkVZX7k3KriHm0i - gitaly: Host Detail
See: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16316