[ENH]: Reduce recall threshold in test_add to 95 (#5254)

## Description of changes

_Summarize the changes made by this PR._

- Improvements & Bug fixes
- We reduced the PL size from 200 to 50 so now we are brute forcing
1/4th of what we used to do before. We also modified the rng_query() to
correctly handle negative distances. Previously for IP, rng pruning
would filter out everything so the code ended up creating a new center
everytime a point was added. Now, it appends to existing centers and
also duplicates the same point to different centers.
- Because of these, test_add is flakey sometimes with recall of < 99 for
high k. One instance was obtained_recall=98% and k=50.
- This PR changes the recall threshold to 95% for test_add which is a
more realistic threshold.
- New functionality
  - ...

## Test plan

_How are these changes tested?_
- [x] Tests pass locally with `pytest` for python, `yarn test` for js,
`cargo test` for rust

## Migration plan
None

## Observability plan
CI flakes are gone

## Documentation Changes
None