gdiplus: fix rounding error (?)

[Vincent Povirk]

That was the worst possible defence of this patch, but I think it
should be included.

What it's actually doing is removing the duplicated logic between the
earlier bit of GdipDrawString, where out-of-range sizes are set to 1
<< 23, and this if statement where we only apply a clipping rectangle
if the sizes are out of range. We could also have added a check for
e.g. scaled_rect.Width >= INT_MAX here, but I think it's better that
we don't duplicate the logic.