Build succeeded despite missing references

[jyasskin]

https://github.com/w3ctag/privacy-principles/actions/runs/3641742327/jobs/6148040286 succeeded even though the "Generate Static HTML" section reported:

[INFO] [Timeout: 10897ms] Processed document.
  Error: ROR] Reference “[Addressing-Cyber-Harassment]” not found.
         Count: 1
        Plugin: core/render-biblio
          Hint: Search for [“Addressing-Cyber-Harassment”]([https://www.specref.org?q=Addressing-Cyber-Harassment](https://www.specref.org/?q=Addressing-Cyber-Harassment)) on Specref to see if it exists or if it’s misspelled.
  Error: ROR] Reference “[Internet-of-Garbage]” not found.
         Count: 1
        Plugin: core/render-biblio
          Hint: Search for [“Internet-of-Garbage”]([https://www.specref.org?q=Internet-of-Garbage](https://www.specref.org/?q=Internet-of-Garbage)) on Specref to see if it exists or if it’s misspelled.
      [INFO] [Timeout: 9889ms] Done.

[sidvishnoi]

https://github.com/w3ctag/privacy-principles/actions/runs/3641742327/workflow#L15 says build should fail on warning only. Feels a bit counter-intuitive I know, but you need to set it to "everything" (which is default). See https://w3c.github.io/spec-prod/#build_fail_on

Would be nice if ReSpec can improve its --fail-on feature to be compatible with Bikeshed.