Docs are duplicated

e.g.,
```
Usage
    Permissions
    Token Authentication
        Managing Tokens
    Permissions
    Token Authentication
        Managing Tokens
```

The links for the first are from `@relengapi`, and for the second are from `relengapi-mapper`.  I think this is because of the namespace packages, with `relengapi/docs` translating to the same path for every dist.  I tested this out locally when I wrote the docs-merging code, but either I didn't replicate the situation correctly, or I'm using different versions of something that work better.
I really wish this could be done programatically on `build-docs` instead of needing user-arg specification