Always Use Most Recently Generated Transcript for Event

With our recent upgrade to the Whisper Speech-to-Text model -- we have sort of deprecated the "confidence" attribute on the Transcript documents. Prior to this change, even if you had backfilled events / reprocessed events with cdp-backend v4, those transcripts might not have shown up because the transcripts were being selected using this old semi-deprecated "confidence" attribute.

We now selected the "most recently created transcript" for the event which hopefully should be the best.