Legal API - Remove/Cleanup old versioning DB artifacts (DO THIS LAST)

After PROD deployment of new DB versioning and if things have been looking good for a while, we want to start removing the code for the old versioning.

That also includes the removal of usage of the feature flags from the code. We will only use the code for the new versioning.

We will keep the feature flags in LD for now. We can remove later once all the cleanup is done.

This ticket takes care of the legal api cleanup.

Need to handle:
- [ ] Clean the old DB artifacts from the legal api
- [ ] Tweak models as necessary
- [ ] db.py might need some updates too to clean up initialization of sqlcontinuum
- [ ] Might need some additional misc. tweaks/removals
- [ ] Verify/test your changes and monitor if something's missing