insights: truncate tables with semantic changes for 3.31 release

Created by: coury-clark

The code insights tables series_points in the codeinsights-db has had a semantic change to how points are stored, and should be cleared with the 3.31 release. The insights_query_runner_jobs in the frontend db has historically been bloated full of useless records that needs to be cleared now that the code insights backend tracks state for series backfill.

Neither of these tables will result in material loss of data, these are by design and definition ephemeral and reproducible.