Fix a couple busted links in CONTRIBUTING.md
Fix a couple busted links in CONTRIBUTING.md

GitHub will not parse Markdown links that do not have '(' directly adjacent to
']'.

Review-Url: https://codereview.chromium.org/2756483004

benschmaus/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,benschmaus/catapult,benschmaus/catapult