Remove SK_IGNORE_MAC_FONT_WEIGHT_FIX.

This is now a dead define, and the changes have been rebased in both
Skia gold and Blink layout tests.

BUG=skia:5095

Cherry-pick: df801aac5f57c64eb7f081288a299fa3c92cee0d
Approved: https://crbug.com/541846#c21
1 file changed