Update test corpus expectations for FreeType roll to f37083edf.

Optimize the modified PNGs while we are at it to save some space.

BUG=pdfium:1295
TBR=drott@chromium.org

Change-Id: I2674ea9965a6ac1d46f2d1900553d09c42af6086
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium_tests/+/56294
Reviewed-by: Lei Zhang <thestig@chromium.org>
740 files changed