Add the Skia expectation for 2_halftone.pdf

Adds the Skia expectation for 2_halftone.pdf as we decide the current
Skia rendering result is acceptable.

Bug: pdfium:1860
Change-Id: Idd932aa90217c25357acb9c4c4d81bc6780dd371
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium_tests/+/103950
Reviewed-by: K. Moon <kmoon@chromium.org>
1 file changed