insights: codeinsights-db on postgres image breaks CI

Created by: coury-clark

When running CI against src/src with the codeinsights-db pointed to plain postgres instead of timescale, CI takes a very long time and fails to pass.

Failing PR: https://github.com/sourcegraph/sourcegraph/pull/32697

From @caugustus-sourcegraph:

I think I’ve discovered part of the reason CI tests are so slow - in our custom postgres image we force a reindex if it hasn’t been done before. This is probably getting triggered on every test and causing everything to be slow - disabling the reindex restores the original test timings.