nanobench: Stop reporting median_ms, it's no better than min_ms.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1825473002

Review URL: https://codereview.chromium.org/1825473002
1 file changed