musicbrainz host, https and ratelimit config options are ignored

### Problem

While trying to make the `mbsync` plugin work with a selfhosted server, I noticed that the ratelimiting was not respected.
Further looking into the issue, I noticed that none of the requests were appearing in my server logs.
Not only that, but when watching the logs while doing a normal import on a fresh installation without any plugins, nothing appears either.

Edit for clarification: Beets continues to work, but sends requests to musicbrainz.org as if I didn't edit the config.

### Setup

* OS: multiple tried, behavior was consistent between NixOS and Arch Linux
* Python version: tried 3.10.5 and 3.10.8 respectively
* beets version: 1.6.0
* Turning off plugins made problem go away (yes/no): no

My configuration (output of `beet config`) is:

```yaml
# beet -c poc.yml config

musicbrainz:
host: mbserver.example.org
https: yes
ratelimit: 100

```

Start by reproducing the issue with the `musicbrainz` configuration shown and inspect the `beet config` output while tracing requests made during a normal import and through the `mbsync` plugin. Done means the configured host, HTTPS setting, and ratelimit are honored, including for a self-hosted server, rather than requests going to musicbrainz.org.

Written by the indexing model from the issue text.