Remove SK_SUPPORT_LEGACY_BITMAP_SAMPLER_BIAS

No longer defined in Chromium.

R=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1568893002

Review URL: https://codereview.chromium.org/1568893002
1 file changed