Buildbucket: fixed links in documentation
Buildbucket: fixed links in documentation

TBR=vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1274113006

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra