The `to_nice_yaml` helper will by default wrap any string YAML values on
the first space after column 80. This can in worst case yield invalid
YAML syntax. More details in Ansible's documentation here:
https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html#formatting-data-yaml-and-json
In short, you need to explicitly provide a custom width argument of a
high number of some kind to avoid the line wrapping.
Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1682
Previously, when matrix-postgres was disabled, we were setting
`matrix_mautrix_twitter_database_engine` to an invalid empty value.
Now, we always hardcode `matrix_mautrix_twitter_database_engine: postgres`,
but set/unset the database hostname and password values instead.
