[pinpoint] Fix typo: s/_attempt_count/_repeat_count
[pinpoint] Fix typo: s/_attempt_count/_repeat_count

TBR=simonhatch@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/3007273002

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult