Add Skia expectations

Adds Skia expectations for 4_36.pdf and new_pdfsign1.pdf, as we've
decided the current Skia results are acceptable.

Bug: pdfium:1859, pdfium:1863
Change-Id: I3c60b650776dd9cab1a5c3c4242192dc00e8fb68
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium_tests/+/103910
Reviewed-by: Nigi <nigi@chromium.org>