lint sample files are out of sync with registry proto

The [StyleGuide proto file](https://github.com/apigee/registry/blob/9d9e8a3b452f1c6956dba044c68b5a7cd7ef39e9/google/cloud/apigeeregistry/v1/style/style_guide.proto) in the main registry repo seems to have diverged from the format expressed in the YAML and generator in [the lint folders](https://github.com/apigee/registry-experimental/tree/main/lint).