The font paths were breaking in IE8 as we since v3 we're no longer postfixing
them with `?#iefix`.

As we removed the EOT files in v3 to stop serving GDS Transport font files to IE8 (see ),
this commit removes the font faces from the IE8 stylesheet. This means that IE8 will fall
back to system fonts, in this case Arial or sans-serif.

Our previous approach of postfixing `?#iefix` wouldn't work here as IE8 would end up
downloading the WOFF files which it cannot render.

The downside of this approach is that the IE8 stylesheet still says
```
font-family: "GDS Transport", Arial, sans-serif;
```
which could be confusing.

An alternative would have been define a new font family for IE8 at the `settings` level.
See https://github.com/alphagov/govuk-frontend/compare/fix-ie8-fonts-alt-approach

This also imports the IE8 tools for testing `govuk-typography-common`.