luci-scheduler: Ensure trigger points to a defined job

See https://chromium.googlesource.com/chromium/src/+/da5f2ead0203a2a866241cb8ac7be53ced7211cf/infra/config/global/luci-scheduler.cfg#61

I typo'ed the job name, pointing it to one that doesn't exist, and the luci-config validation presubmit let it go through.