Angle brackets are converted to HTML entities rather than passed through for shortcodes

https://github.com/istio/api/blob/master/security/v1/peer_authentication.proto:

```
// {{< warning >}}
// Development of PeerAuthentication is currently frozen and likely to be replaced in Ambient.
// {{< /warning >}}
```

https://github.com/istio/api/blob/master/security/v1beta1/peer_authentication.pb.html:

```

{{< warning >}}
Development of PeerAuthentication is currently frozen and likely to be replaced in Ambient.
{{< /warning >}}
```

[The shortcodes don't work on the site as a result](https://deploy-preview-14981--preliminary-istio.netlify.app/latest/docs/reference/config/security/peer_authentication/).

Can we change the parsing, or should we remove the shortcodes?