Fix non-JS login check

The non-JS login check (using a 1x1 pixel image) was supplying an
unnecessary "from" parameter, which was causing a false positive on the
check added in Ife44d285. Since that "from" parameter is unnecessary,
we can just remove it.

Bug: 52356
Change-Id: I38134389b891dc1f07f536c84a1e827c4e16848c