[BUG] Fix connection in scraper

[dwreeves]

Overview

On Unix systems, the script in /backend/scraper/mapping_police_violence.py doesn't work due to SSL cert issues via OpenSSL. This will be a barrier to integrating into Heroku easily with automatic filling of data as a postdeploy script. It's also a pain for me personally and a couple other volunteers, and makes it hard to contribute.

My recommendation is to download the xlsx file manually and load from that (as a hotfix), then once that's done we can create a separate issue that's about making the process more automated while dodging the SSL cert issues.

Requirements for issue:

• Make the script load from a local version of xlsx.
• Create new Github issue outlining a feature request for fixing the SSL cert issue.