Docs: ooops, debug is the default in GN.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2195173002
NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=2195173002

TBR=jcgregorio@google.com

Review-Url: https://codereview.chromium.org/2195173002
1 file changed