check_category and metadata_vs_api are very similar

For both of them:

```
description = (
"This script compares the info on local METADATA.pb files"
" with data fetched from the Google Fonts Developer API.\n\n"
" In order to use it you need to provide an API key."
)
```

and there's a lot of common code. We need to choose one and kill the other. `metadata_vs_api` looks more complete.