I'm worried about this messing with unrelated span tags that have nothing to do with this font-weight bug. There are valid reasons for a header to have a span eg. `<h2>Pull Request <span class="pull-request-id">390</span></h2>`

A strategy that would fix this without potentially stripping unrelated spans (and that might fix related issues in non-header elements) would be:

1. Only do this if the `cmd` was bold
1. If the `tagName` is span, the span has no classes and the span has a `style` of `font-weight: normal`, only then should we unwrap it.

Thoughts?