Generate grammar fails on first attempt with experimental formatter

[datho7561]

1. Clear the lemminx cache
2. Use the experimental formatter
3. Make an XML file with some content that is not associated with any schema
4. Use the "generate schema and associate" quick fix (you should be able to use any of the generate quick fixes)
5. Nothing will happen
   In the logs, you should see a org.eclipse.lemminx.uriresolver.CacheResourceDownloadingException.
6. Try again, this time it should succeed.