[BUG] `server/vector_index.pkl` listed in .gitignore, but still in repo

[calumbell]

Bug description

The server/vector_index.pkl is listed in this repository's .gitignore but is nonetheless included in the repo. This is likely due to the file being commited before being added to the .gitignore. server/vector_index.pkl should be removed (it gets rewritten whenever the search index is generated, ie. manage.py quicksetup)

This file being part of the repo quite often causes errors to be thrown when switching between branches on local with DB variations:

error: Your local changes to the following files would be overwritten by checkout:
server/vector_index.pkl
Please commit your changes or stash them before you switch branches.
Aborting

Steps to Reproduce

1. View the .gitignore, server/vector_index.pkl is explicitly excluded
2. Open at the server folder, and look who is there.