OKF log.md file can have a frontmatter ?

From what I understood in 0.1 & 0.2 specs, `log.md` files should not have frontmatter ?

But the [log.md](https://github.com/GoogleCloudPlatform/knowledge-catalog/blob/main/okf/bundles/acme_retail/log.md) provided in the the `acme_retail` provided example has one:
```yaml
---
type: Log
title: Acme Retail bundle history
---
```

Start with the linked okf/bundles/acme_retail/log.md file and compare its frontmatter with the 0.1 and 0.2 specifications referenced in the issue. Confirm the intended rule, then update the example or specification so they agree and verify that no other log.md examples contradict it.

Written by the indexing model from the issue text.