Eventlog: Fix whitespace after embedded eventlog html

We embed the eventlog2html plots directly into the eventlog chapter which gives us nice interactive plots, but for some reason this leaves whitespace after each embedded plot.

The whitespace is not an html element and from reading the internet is related to how `iframe`s are laid out. So this is a css issue that is induced by these webkit lines:

```
#scaled-frame {
zoom: 1.00;
-moz-transform: scale(0.75);
-moz-transform-origin: 0 0;
-o-transform: scale(0.75);
-o-transform-origin: 0 0;
-webkit-transform: scale(0.75);
-webkit-transform-origin: 0 0;
}

```

in `/hs-opt-handbook.github.io/_static/css/iframe.css`