25056: backport-1.0: build: GH label changes r=jordanlewis a=jordanlewis

Backport 1/1 commits from #25050.

/cc @cockroachdb/release

---

- Robot -> O-robot
- test-failure -> C-test-failure

@benesch do we need to backport this for it to work on other branches?

Release note: None



Co-authored-by: Jordan Lewis <jordanthelewis@gmail.com>