Update corpus expectations for axial shading incremental stepping

Updates AGG expectations for 4_2, shading, shading1, and shading_2_8
for the affine stepping optimization in
https://pdfium-review.googlesource.com/c/pdfium/+/161830.

Bug: 42270903
Change-Id: I8a4306132ccdd81c5c4197c1d6817b3bd120c119
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium_tests/+/161850
Reviewed-by: Lei Zhang <thestig@chromium.org>

fx/mulobj/4/4_2_expected.pdf.0.png

diff --git a/fx/mulobj/4/4_2_expected.pdf.0.png b/fx/mulobj/4/4_2_expected.pdf.0.png
index cd75c70..f49b883 100644
--- a/fx/mulobj/4/4_2_expected.pdf.0.png
+++ b/fx/mulobj/4/4_2_expected.pdf.0.png
Binary files differ

fx/new/shading_2/shading1_expected.pdf.0.png

diff --git a/fx/new/shading_2/shading1_expected.pdf.0.png b/fx/new/shading_2/shading1_expected.pdf.0.png
index ebb7c2f..5b61954 100644
--- a/fx/new/shading_2/shading1_expected.pdf.0.png
+++ b/fx/new/shading_2/shading1_expected.pdf.0.png
Binary files differ

fx/new/shading_2/shading_2_8_expected.pdf.0.png

diff --git a/fx/new/shading_2/shading_2_8_expected.pdf.0.png b/fx/new/shading_2/shading_2_8_expected.pdf.0.png
index 7fc2da6..e4f915d 100644
--- a/fx/new/shading_2/shading_2_8_expected.pdf.0.png
+++ b/fx/new/shading_2/shading_2_8_expected.pdf.0.png
Binary files differ

fx/new/shading_2/shading_expected.pdf.0.png

diff --git a/fx/new/shading_2/shading_expected.pdf.0.png b/fx/new/shading_2/shading_expected.pdf.0.png
index 13090b8..95b9710 100644
--- a/fx/new/shading_2/shading_expected.pdf.0.png
+++ b/fx/new/shading_2/shading_expected.pdf.0.png
Binary files differ