Revert "svgtiny: update source url"

This reverts commit 8f9b5f65.

The new svgtiny version does not build at all, see:

  http://autobuild.buildroot.org/results/242/24257e9739df8f589150336cb6213812516bf465/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>