While we worked on T353798: Fix the data collection for ReferencePreviews, we needed to change the schema and started collecting events for the baseline in with the monoschema[1][2] approach.

The baseline data we now collect under mediawiki.reference_previews needs to be wired into the graphs in Superset.

[1] https://wikitech.wikimedia.org/wiki/Metrics_Platform/Event_Schema
[2] https://gerrit.wikimedia.org/g/operations/mediawiki-config/+/0e7a8158957e6eed9373d0dd15bcb203ac463012/wmf-config/ext-EventStreamConfig.php#1043