windows: block Arial Narrow

This is the only enumerated font that can split users in windows. It's more easily exposed in FontFace with #43322 (closed) but isn't adding entropy. You could always detect it with font-family, it's just slightly tricky with knowing what to compare it to and how/if to set a font weight etc.

FYI the font comes courtesy of MS Office (don't ask me what versions) - given I have it on my windows 7 and I could for example have upgraded to 10 .. we can assume some users will have it