Shrink linear-gradient and text-pattern test outuput.
The real motivation for this is to hide an annoying difference in the
gradient output that occurs when under the influence of a device
offsets. My opinion is that the gradient output should not change due
to just an integer offset, but we currently don't have a precise
gradient specification, so this minor deviation really isn't relevant.
A better fix for this might have been to make the test suite more
forgiving of tiny differences, (perhaps on a per-test basis), but
another advantage of shrinking these tests is that they now run a lot
faster.
It is true that these tests now also exercise fewer different output
values, but that's not the designed purpose of the tests so I don't
feel bad about losing that characteristic.
