bytesHtmlDoc is 0 since 2024-11-01

From @dwsmart in Slack.

It looks like [we only set this for `firstHtml`](https://github.com/HTTPArchive/wptagent/blob/6eae276cc37b136a6ea260def24be6927e748be4/HTTPArchive/transformation.py#L507) but I can't see this being set. It looks like we only set `first_html` and `first_html-url`.

Maybe this is code that wasn't migrated properly from the old way of doing this?