Nethealth dashboards added from this repo stop detecting the datasource

For example https://grafana2.torproject.org/d/churn_lost_new/relays-churn-lost-and-new?orgId=1&refresh=1d, The code defines the postgres datasource as a variable (https://gitlab.torproject.org/tpo/tpa/grafana-dashboards/-/blob/bc1b1a0a54d7d03324bda0ba49127ab60331250a/network-health/relays-churn-lost-new.json), i think this is generated when exporting the dashboard to share externally. The variable is not visible when looking at the JSON Model in the dashboard settings (https://grafana2.torproject.org/d/churn_lost_new/relays-churn-lost-and-new?orgId=1&refresh=1d&editview=dashboard_json) and i thought it might be that, but it was working before. It could also be that grafana version as changed. In the code it's 10.1.4 and the one running is v11.1.3. Maybe is that?

I've manually imported the same json that there's in this repo to another dashboard, removing the versions but leaving the datasource variable. However, when looking at the JSON Model in the settings (https://grafana2.torproject.org/d/churn_lost_new2/relays-churn-lost-and-new-2?orgId=1&refresh=1d&editview=dashboard_json) uses the uid of the datasource instead of the variable. The variable is well defined when exporting this dashboard.

We should figure out whether there's a way to add the exported dashboards in this repo so that they continue working when updating grafana to a new version.