Modify launch.md to recommend metrics2
Modify launch.md to recommend metrics2

NOTRY=true
BUG=skia:4899

Review URL: https://codereview.chromium.org/1729303002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot