As a developer I want to remove support for the deprecated YAML database format so that there will be less vestigial code to maintain.

Rationale

In #2189 we changed the database format from YAML to JSON for performance reasons. To ease the transition for users the PR made it possible to read the old YAML format and output the new JSON one transparently. Since the change happened three years ago, it's probably safe to remove the code that takes care of this conversion in database.py.

Description

The idea is to just go through the database.py module and remove any reference to the old database file and related code. Might also impact unit tests.

Additional information

None