dm: gamma_correct: true/false -> "yes"/"no"

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1755693002

NOTREECHECKS=true

Review URL: https://codereview.chromium.org/1755693002
1 file changed