Remove IncludeDocsLink from bufconfig.BufYAMLFile

[bufdev]

This is a write-only property that has nothing to do with the BufYAMLFile interface and what this object is. We need to rewrite https://github.com/bufbuild/buf/pull/3181 so as to not add this method to BufYAMLFile, which shouldn't be that bad - it should just be an option PutBufYAMLFileForPrefixWithIncludeDocsLink.