The function lookup/synonyms doesn't work (no thesaurus backend is available)

### What did you expect to happen?

I've configured Doom Emacs to use in init.el to use (lookup +dictionary +offline), following the [documentation](https://docs.doomemacs.org/latest/modules/tools/lookup/).

Running lookup/synonyms keeps telling me that no thesaurus backend is available.

Is there a dependency or configuration option that I am missing?

### What actually happened?

lookup/synonyms keeps telling me that no thesaurus backend is available, and does not produce a result.

### Describe your attempts to resolve the issue

I have also installed wordnet and ripgrep via Homebrew, and synced Doom Emacs and ran reload. I'm on Mac OS X.

While lookup/dictionary-definition works (with osx-dictionary), lookup/synonyms just tells me that no thesaurus backend is available.

### Steps to reproduce

Open Doom Emacs. Install lookup with dictionary option (and possibly +offline). Try to run lookup/synonyms. It will tell you that no thesaurus backend is available.

### System Information

https://pastebin.com/CipwNYK2