check-by-name: Update .envrc to remove deprecated command

Noticed the following warning:

```
direnv: `nix_direnv_watch_file` is deprecated - use `watch_file`
```

Which seems to come from here:

https://github.com/nix-community/nix-direnv/blob/6455f38a8dcf731dccd69aabef3f85ac962bfa8d/direnvrc#L207



Seems this check is no longer needed

check-by-name: Remove check from .envrc

Co-authored-by: Silvan Mosberger <github@infinisil.com>