Revert "smaller viewport for Kobo H2O (bezel overlaps bottom)"

This reverts commit fc36d6db371a79e9500eea426a4f4d11ec9dbafb.
Sorry, the bug description was misleading. The problem is rather that the font became too large, so it reaches over the (imaginary) baseline. See here: https://github.com/hwhw/koreader/commit/fc36d6db371a79e9500eea426a4f4d11ec9dbafb#commitcomment-8752241