Do not fail pull requests from forks on trigger-detector-benchmarks

[wdconinc]

Is your feature request related to a problem? Please describe.
Pull requests from a fork do not have access to the secrets necessary to trigger eicweb benchmarks in the trigger-detector-benchmarks job, and consequently that job fails, e.g. #61. There is no way to 'unfail' this job without going through the API.

Describe the solution you'd like
We should succeed the trigger-detector-benchmarks job, but use it to set the eicweb/detector-benchmarks status to pending. This way, the status will remain pending until someone starts the pipeline by hand, at which point the pipeline will succeed and no remaining failed jobs remain

Describe alternatives you've considered
No other alternatives considered...