gitgud deltas need to be recalculated

There was a bug: https://github.com/cheran-senthil/TLE/commit/8b580a3e5d188a1f67209dfbf30e082cae47ec4a

So we need to go through the database and change the delta to problem.rating - round(user.rating[at issue_time], -2) and then recalculate points.
Shouldn't be too hard.

Start by locating the database records and code that calculate GitGud deltas and points, then review commit 8b580a3e5d188a1f67209dfbf30e082cae47ec4a for the original bug. Recalculate each delta from the problem rating and the user's rating at issue time, then verify that points are recalculated consistently across the affected records.

Written by the indexing model from the issue text.