Remove the struck-out items in METRICS.md that were never implemented or became moot
Remove the struck-out items in METRICS.md that were never implemented or became moot

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