Rollup merge of #122698 - clubby789:cancel-hourly-update, r=Mark-Simulacrum

Cancel `cargo update` job if there's no updates

Previously there were always updates so we didn't hit this. Since #122489, this job runs on a more frequent schedule and causes errors if there have been no changes in that timespan.

This led to a weird error on rust-lang/rust#122646 (comment) - because of this I've replaced the `exit 1`s here with `gh run cancel` so we don't have false 'failed' jobs in the logs.

Author: matthiaskrgr