[qutebrowser] Font issues

[N/A]

I'm having a minor problem. On some websites (Github on any page other
than the 'home page' comes to mind), it uses a font I haven't
specified. I have attached a screenshot, or at least attempted to. The
font appears to have no antialiasing, which makes it look bad
especially when bold. I've tried changing the options for fonts in
qute://settings, but none seem to have any effect on it. How can I
change it?