Fix #2134, remove images from METRICS.md
Fix #2134, remove images from METRICS.md

mozilla-services/pageshot,mozilla-services/pageshot,fzzzy/pageshot,mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/pageshot,fzzzy/pageshot,mozilla-services/screenshots,mozilla-services/pageshot,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/screenshots