Code review comment for lp:~joni-noplu/elisa/teletext_fix

I have already tweaked accordingly and merged Jonathan's branch.

@Michał: yes, I though of that too, but it looked overkill until we have more than one mime type we want to filter out. At that point we'll need to implement your idea or something similar.

@Paul: I had missed this one in my review, but I fixed it before pushing. All good!