Remove SK_SUPPORT_LEGACY_SAMPLER_BIAS

The guard has been removed from Chromium, this is now dead code.

TBR=reed@google.com,caryclark@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1658563002

Review URL: https://codereview.chromium.org/1658563002
1 file changed