insights: LineChart click through diff search for scoped but backfilled insights incorrect

Created by: chwarwick

When clicking on a LineChart Point to see the diff search for an insight over some repos that has been backfilled, and incorrect diff search is generated in that it did not scope the search to the repos for the insight.

A series scoped to a single repo with a search query of: <LineChart -file:.story -file:README.md lang:TSX patterntype:regexp

Generated the following diff search:

https://{ENV_URL}/search?q=type:diff+after:2022-04-05T20:00:00-04:00+before:2022-04-19T20:00:00-04:00+%3CLineChart+-file:.story+-file:README.md+lang:TSX&patternType=regexp