Update webhook-rocket.rs

[JBlashME]

Outcome does not have Failure just Error event_type does not exist in Event changed to type_ def

Summary

Checklist

I was unable to run these. Sorry I am new to rust and I really appreciate the work done on this project. I can't figure out how to delete this so thought id open the PR. If this is wrong we can just delete it and when I get better I can reopen the PR

• [ ] ran cargo make fmt
• [ ] using conventional commits to hightlight user-facing fixes and features

[arlyon]

Ah, yeah, it looks like our rocket example has slipped through CI... I will see if I can add a job to run that also so that it doesn't silently break again.