fast/text/atsui-small-caps-punctuation-size.html is flaky on Mac

Unreviewed gardening

BUG=419486
TBR=eustas@chromium.org

Review URL: https://codereview.chromium.org/614423003

git-svn-id: svn://svn.chromium.org/blink/trunk@183077 bbb929c8-8fbe-4397-9dbb-9b2b20218538