Please unblock package unknown-horizons

This updates fixes #1033833: the package font-unifont
dropped shipping unifont.ttf last summer, and this breaks
unknown-horizons/2019.1-5 as the symlink to the font is no
longer valid and the game fails to load.

The update fixes the symlink to the otf font, which works
with the game as well.

[ Impact ]
Game would be broken.

[ Risks ]
This game is a leaf package.

[ Checklist ]
  [X] all changes are documented in the d/changelog
  [X] I reviewed all changes and I approve them
  [X] attach debdiff against the package in testing

unblock unknown-horizons/2019.1-6

Unblocked.