Emailer - Remove/Cleanup old versioning DB artifacts

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 emailer cleanup.

Need to handle:
- [ ] Clean the old DB artifacts from the emailer
- [ ] Might need some additional misc. tweaks/removals
- [ ] Verify/test your changes and monitor if something's missing

Start by locating the emailer code that handles the old and new DB versioning, then identify its feature-flag usage and related artifacts. Done means the old DB artifacts and code-level flag usage are removed, while the LaunchDarkly flags remain; verify and test the changes and monitor for missing cleanup.

Written by the indexing model from the issue text.