Fixes #576

Now it correctly results in the error message:

```
There was an error interpreting Starlark code 
Evaluation error: fail: Unsupported launcher 'foo', need one of 'lighthouse,lodestar,nimbus,prysm,teku,grandine'
        at [github.com/kurtosis-tech/ethereum-package/main.star:104:55]: run
        at [github.com/kurtosis-tech/ethereum-package/src/participant_network.star:166:34]: launch_participant_network
        at [github.com/kurtosis-tech/ethereum-package/src/cl/cl_launcher.star:106:17]: launch
        at [0:0]: fail

Error encountered running Starlark code.
```