Revert font stack to be just sans-serif

This is a follow-up to I0865d144c70a726eb97b42a247d32131463bb6df
and I555862a3c64cd08f5755b9ba1d63450a5186dd73. To understand why
this changes again see Ibcdaff0174d526c5411aa88aea8b1dbc088372ee.

Change-Id: Ie0284b52a08b9541e5a277ed5ab67e58ac135fd8