remove legacy flags from g3

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4225

Change-Id: Icb3e8f132975d1ef2b6b89de05b49f89e2424f78
Reviewed-on: https://skia-review.googlesource.com/4225
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed